I honestly do find it a curious puzzle why this one class, in one specific form, is so precious to some players.
It does something well that the game never did at all well before. But, it's not just that the game didn't do a lot of martial concepts well - it doesn't do many caster concepts well, either, due to Vancian being so un-genre, for instance - but that it also did them in a way that was very disappointing or underwhelming or under-contributing or 'low' agency, depending on how RPG-theory you want to get in expressing what boils down to suck.
When I played magic-users back in the day, I noticed that they were nothing like wizards or sorcerers or anything else in any fantasy book I read or movie I watched. But they were still fun to play, the Vancian mechanic was a very game-worthy puzzle - you tried to pick the bests spells for the day based on what you know or could infer about the coming adventure. That's a fun little mini-game or meta-game. And, when you do pick the right spells, spells really do something. Perhaps most importantly, even though the mechanics for memorizing spells were alien to the genre, you could imagine they were just an abstract player-driven way of handling more arbitrary and genre author-force things like 'the stars being right' or 'laws of magic' or 'attracting the attention of terrible forces' or whatever, that keeps wizards from just doing whatever they want, instead of only what the author wants them to be able to do to move the story along -
and you still seemed like you were using magic. And, that also all applied even at 1st level - you may have had only 1 spell, but when you used it, you were doing magic, because you decided to play a character who could do magic, and you decided when that magic would happen. Today, we call that a lot of things, like 'player agency,' and whatnot, but it's really just getting to play the character you want.
When you played a fighter, OTOH - and the result of this was that, after a couple of times, I just didn't - if you had this vision of medieval knight or, really, a lot of the characters you'd see in fiction or fantasy or myth or even history - he'd be fighting with a sword in exciting, dramatic duels, or jousting or repelling a siege, defending a village, fighting a battle and so forth. If you waited to 9th level, you'd get a few men at arms and be able to build a keep and do some of that. Until then, you'd be wandering around in dungeons, standing between monsters and the rest of the party while the cleric healed you. Your dramatic sword-fights were a dice roll or two, if you wanted to disarm you needed to use some pole-arm you never heard of, and that only if you convinced the DM that the footnote on the weapon table was a real rule, and when you did get those men at arms, they barely rose to the level of red-shirts. It didn't get a lot better for a long time.
But it did get better. In 3e the fighter got lots of bonus feats and you could really customize it. Your sword-fights (or, wierdly, spiked-chain-fights) got a bit more dramatic. You were closer to playing the character you envisioned, though it was all too likely that before very many levels, nothing you did would matter much compared to what some CoDzilla was doing. But it was a big step in the right directly. You could even take Leadership, which, again, maybe gave you a few redshirts, but also one pretty good henchmen - though, the best thing for it to be was probably a caster of some sort. Also, there were a couple of other non-casters, and you could mix & match, so build-to-concept was very much there, viability was the big stumbling block. But the weird part was the way that 3e called out the fighter as the frequent 'party leader,' (as opposed to face) while giving him /nothing/ mechanically to back it up.
In 4e, the fighter was balanced, but it's role was constricted down to a very specific function not unlike standing between the party and some monsters just like in the olden days - it still got lots of cool stuff to do while fulfilling that function, meat-shield function though it was. But, the Warlord was the more militant, functional useful leader the 'Lord' and fighter-as-party-anchoring-leader never delivered on. It stepped into a re-imagined role (broader than just healer) that had previously only been filled by casters and was competitive in that role.
4e brought the martial classes up to par for the first time in the game's history. Casters could still do more, especially out of combat, but the gap wasn't profound anymore. You could play a martial character and 'have agency' make real /and even varied/ contributions, make decisions that mattered, and generally not be overshadowed, and, as had always been the case with casters, be able to play the character you envisioned meaningfully from level 1. That wasn't just because of the Warlord - the Fighter, Ranger, and Rogue, within their roles, were also balanced and viable.
5e comes along, and the Ranger is back to being a caster, the Fighter (if he doesn't cast spells) is back to 2e-style high-DPR - which vaguely balances the class and gives him a real contribution to make in combat, but very little in the way of meaningful choices, build-to-concept, or 'agency' (whatever you do with your fighter, you either contribute DPR, or under-contribute radically), and the Rogue is back to 3.x style out-of-combat contribution + SA in combat. The Rogue probably got the least worst deal, but if you wanted to play a martial concept, you weren't much better off (unless you really wanted to play a thief or assassin) than you would have been in AD&D.
So, the Warlord is what's left to open up 5e to some good martial concepts. That's what I find particularly special about it in this context. In the context of it's introduction, it made a concept that had never worked well before work well and in a balanced way, both in terms of the RP/'fluff,' and the implementation and contributions it could make.
I think the analogy to Illusionists is a great example: some people liked it as its own class, and the Illusionist sub-class bears almost no resemblance to that original class, and yet you don't find 100 page vitriolic threads about Illusionists.
That happened back in 2e though. Anyone who was bothered by the Illusionist going from Magic-User Sub-Class to Specialist Wizard has had 26 years to get used to it.
And, while the illusionist as a specialist doesn't bear a strong resemblance to the original, it's mostly because it's become so much /better/. From topping out at 7th level spells, to full 9 spell level progression, from casting 1 spell at first to cast more spells at first than if he didn't have a specialty, to specialties being mandatory & having at-will cantrips and extra features for being an Illusionist. Who's going to complain about that?
Well, [MENTION=6801328]Elfcrusher[/MENTION], could it possibly be that A) We have a full Illusionist class in 5e, complete with pretty much everything a 1e Illusionist could do, plus more or B) there is a larger contingent of players who want a warlord class than an illusionist class or C) both of the above?
(A) it's a specialty, you choose it at 1st so it's a lot more like a class than most sub-classes, but it's still not a class in it's own right. Of course, it never appeared as a full class, in 1e, it was also a sub-class. (B) I've seen nothing to indicate that, if the Illusionist specialty didn't exist, there'd be fewer people wanting it than want the Warlord (or more, really it's one of those numbers no one's got any data on).
If you want a very similar discussion to this one, surf back a few months at En World and look at the Psionicist threads. Only difference is, the Psionicist crowd GOT what they wanted - a full Psion class. Every single argument applied to Warlords equally applies to Psions. So, pretty much, the arguments against warlords hold about as much water as the ones agains Psions. IOW, none.
Psionics are a science-fiction bit that lets authors in that genre use themes and story elements from myth, folklore and fantasy that involve magic. They're magic with the serial numbers filed off for use outside the fantasy genre. Used within the fantasy genre, they evoke that that science-fiction feel /and/ are redundant, doing nothing magic cannot, and doing it in a supernatural way not meaningfully different from magic. That's a much stronger argument against psionics than any leveled against the warlord. It still doesn't hold water, though.
But, out of curiosity, what does a 1e Illusionist have that a 5e one does not? Other than the fact that 5e uses a somewhat different casting system, what spells or abilities does an illusionist have from previous editions that is missing from 5e?
It's what's not missing. The 1e Illusionists spell list was a lot smaller and more heavily focused on illusions, very little that he did was 'real.' A 2e or 3e Illusionist specialist could cast a much wider range of spells than a 1e illusionist sub-class. A 5e specialist, IIRC, doesn't have opposition schools, at all. A purist could complain that the Illusionist is 'too good to be a real illusionist.' Heck, you could complain that the wizard is too much caster for any character concept, because it is so flexible in what spells it can cast that, given similar knowledge of coming challenges, any two wizards are likely to show up with very similar slates of spells and play very similarly. That's being a different kind of purist, though.
I can think of lots of arguments against warlords that don't apply to psions, except nobody seems to want to hear/believe my arguments. Psions don't encroach mechanically on intra-party social dynamics, or impinge on the player's right to describe his own character's mental states.
They have telepathy and mind control. They can /literally/ do that stuff. I don't think anyone had the temerity to bring up an objection like that, though. It is a really weak objection, since it relies on both hypothetical players being unable to handle the most basic aspects of participating in an RPG.
Nor does "Psion" describe an earned title. It's a one-word description of their trademark abilities, not a role to which they aspire.
That is a meaningless objection. The Psion name and psionic concept evokes another genre, entirely, a much worse problem. But, name-based objections are pretty pointless, there are problems with any name.
And no form of psionics currently exists in any base class, sub-class, or feat.
There are many classes that perform telekinesis, inflict psychic damage, dominate, levitate, etc... Everything a psion could do can already be done by some other caster. You could re-skin Sorcerer or Warlock (especially a GOO Warlock) to be a psion.
Psionics has also been around much, much longer than Warlords. (I'm not saying that should be relevant, but you are arguing that "every argument that applies to one applies to the other".)
There you go. A very similar argument, though, is that the Psion has never been in a PH1. It's even a stronger argument, since there was that playtest idea they were working from that classes not in a past PH1 weren't on the table for the 5e PH.
But, most importantly, the Psionics threads achieve nowhere near the epic status of the Warlord threads
Why that's the case was the question.
, nor are Psionics fans as intransigent in their views about what the class must include.
They're just as set in their ideas about exactly what psionics need to be. Psionics being or not being magic (and what that implies) is every bit as contentious in psionics debates as Inspiring Word as hp-restoration vs temp-hps is in warlord debates.