Seems to me like [MENTION=12731]CapnZapp[/MENTION] would be happier with 4th edition. I don't mean that as anything other than exactly what it sounds like.
Dismissive edition warring? ;P
Seriously, though, the Capn has not been shy about is 3.5/PF pedigree. So you're way off base.
My interpretation of 4e (Full Disclosure: I have NEVER played 4e...only read) is that it pretty much erred on the side of "DPS Balance" over "Interesting Thing".
Well, try playing it for 10 years and get back to us when you know what you're talking about.
I get that some people like their D&D "crunchy", no problem there. What I don't get is trying to force 5e to be "crunchy" and at the same time remove one of the biggest cornerstones of the game's design: The DM's requirement to be actively involved in adjudicating case-by-case situations with "rulings, not rules".
That's actually critical to such 'crunchiness,' because if you don't know what you're going to get for sorting through all the chaff & trap choices in your crunchy-system-mastery-rewarding game, all that crunch is meaningless. You might as well just let the DM tell you a story, from that perspective.
In 3.x/PF, the DM had this 'Rule 0' dangled in front of him, promising him some latitude in how he ran his game, but, in practice, with a RAW-obsessed fan-base, dismissive of house rules and willing to argue any ruling to death, the mechanics - the consensus on what RAW said about them, ruled the day. And, again, that was critical to the RAW/'build'/optimization culture that surrounded the game.
Of course, 'balance' had nothing much to do with it - the point was extracting all the best, most imbalanced bits. But asking for greater imbalance would probably draw even more acrimony.
I don't accept the validity of this assumption. The primary role of martial characters is to protect the party. Thus they are primarily defined by their ability to not die and to divert attention form the spellcasters.
Sadly they're really bad at both those things. The baseline fighter has one fairly minor self-heal (starts nice, but doesn't keep up), heavy armor proficiency, and, on average, +1 hp per level to "not die." It has nothing (except, well, doing damage, but you don't consider that their thing) to divert attention from the spellcasters (every class casts spells in at least one sub-class, but we get the idea). OTOH, before sub-class even comes into it, the fighter gets more Extra Attacks than everyone else and Action Surge to double those attacks 1rnd/rest, and sure, plenty of high-damage weapons to choose from, for DPR. Barbarians and Rogues (the other two classes that use weapons and have some sub-classes that don't cast spells - ie 'martials'), similarly, have their major combat features (SA & rage) pointed straight at DPR.
Now, a Paladin does use weapons, and can be pretty good at protecting allies - in addition to the same armor, weapons & hps as the fighter, he has healing he can use on himself or allies, and an aura that boosts his & ally's saves. And all paladins cast spells, of course, so they're among "the spellcasters," themselves, rather than "the martials" (or they're "divine gish" if you want, I suppose).
Not that DPR is a great way to try to keep a class relevant, by itself. IMHO/X, when you try to get by with just DPR, you end up either under-contributing (yeah, you're grinding things, but so's everyone, if not quite as hard, and your efforts don't stand out), or over-powered (wow, that's just too much damage, you powergaming GWM, you).
You seem to be talking about the "tank" archetype (tank, damage dealer, healer), but D&D is not set up that way. I believe there are existing threads on this subject..
He's really talking more 'defender,' which 5e barely nods to. 'Tank' is much more 5e-plausible, and how the fighter 'defended' back in the day. The lynchpin of the Tank function: high DPR. With no 'aggro' or marks or anything, you need to just hit the enemy so hard they don't dare ignore you. The fighter, sufficiently optimized for DPR, should be well-able to do that, and maybe even be tough enough to stand up to the consequences for a round longer than the next guy.
Surely, we can constructively criticize rules that invite abuse without throwing all of the solutions on the D.M.
Well, you can criticize them. But the more constructive thing to do is very often for the DM to adjust the campaign to avoid the problem, rather than trying to address that critique. So, while I admit that /just/ volunteering that you have no problem so it must be a DM problem is non-constructive, presenting campaign strategies that might ameliorate intractable issues with the system can be at least as constructive as pointing out those issues (though, really, after 44 years, both the issues and the campaign-tweaking solutions are pretty broadly known).
Zapp could just dial up encounters, drop the odd OP magic item on anyone who didn't take an OP enough build, and ditch xp so that those hugely overleveled encounters don't kick advancement into overdrive. Compared to trying to line-item-veto and amend D&D into a neatly balanced/playable game with a wealth of meaningful/viable choices and a dearth of 'traps' or chaff to sort through, that'd just be orders of magnitudes easier.