I think the analogy is very apt. Yes, 90% of what I want out of the ninja class (from previous editions) can be covered by a few classes in 5e. Just like 90% of what people want out of the warlord can be covered by other classes in 5e. In both cases, you'd have to mix-match classes and feats to get what want, and as you say, there would be in-coherency and wasted build components. And in both cases 10% just doesn't appear at all in 5e. For example, there is no 5e subclass where I as a ninja can change my tracks, hold my breath for long periods of time, walk on water, or other core ninja abilities from previous editions.
Before you say, "Yeah, but you're talking about what YOU want, and not the ninja in general", I'll point out that in all of these warlord threads, there is no consensus as to just what the warlord should look like, so again, the parallels are there (going by someone's personal preference as opposed to in general).
Ironically, what your post did was what has been pissing off the warlord fans for a long time: Someone coming in and saying, "You have your warlord in the game already, just pull bits from this class, and bits from that class, etc, etc"
There is no irony in what I posted. I don't care whatsoever if WotC decides to make a new class called Ninja. Means nothing to me. I actually don't care if they make a Warlord either. And I don't care if you start 5000 posts and a grass-roots movement for them to do so (same as I don't care about a Warlord effort to do so).
What I do care about is an attempt to make an ethical equivalence and then shame others/virtue signal ("My grievance is identical to your own and look at well-behaved I am by comparison!") based off a comparison that isn't remotely like to like.
There is no "core ability" to change tracks in prior editions.
False Tracks was a 1st level spell that the Ninja Kit Spirit Warrior, Shinobi Mage, and Shinobi Illusionist had access to (I remember it quite well as Spirit Warriors were one of the played Ninjas in a prior campaign). I think maybe that was in an AD&D2e Ninja kit perhaps? 5e has
Pass Without Trace for the Shadow Monk. Walking on water can be handled by the Ability Check mechanics. A Rogue/Monk with Expertise Acrobatics should be able to pull that off. Holding your breath for extraordinary long periods of time would be handled by a Con Ability Check. Conversely, both walking on water and holding your breath for Infil/Exfil could easily be handled by Tool proficiency (Ninja) as this is how Ninjas accomplished this in the real world. They're so specialty and so trivially handled I didn't mention them. I also didn't mention Clan Followers.
Everything is there for Ninjas in this edition. Shadow Monk specifically calls them Ninjas (or Shadowdancers) in the description and goes through all the fluff. You don't even have to spec into Rogue/Assassin if you don't want to. You have pretty much everything you need just in Shadow Monk. Personally, I would do it for Assassinate, Expertise, Uncanny Dodge (and you could trivially refluff Thieves Cant to Clan Signs), but that is just me.
I GMed 2 Ninja fanatics in AD&D1e and AD&D2e for about 6 years. They literally played nothing_but_ninjas and so all of my games where they were players featured the relevant thematic material/conflicts. If those guys were still playing with me, they would be drooling over the 5e Ninja (if they're still playing and they're playing 5e, I'm sure they are).The 5e Shadow Monk and the the Shadow Monk/Rogue:Assassin combo is everything those ninjas were but a million times better. You have complete mechanical and thematic coherency. All wheat. No chaffe. And the wheat that you have is many times over more capable, competent, and flat out cooler than that which was in AD&D 1e OA and 2e's CNH.
My first 1-30 4e game featured a Warlord of the 3 PCs. The player that played it is one of my primary players. It is trivially obvious to her, to anyone who earnestly and sincerely played or GMed 4e for any length of time, that there is no 5e Warlord analogue that is mechanically robust/coherent or thematically coherent. Nothing under the Fighter chassis could even attempt to do it because the mechanical design space of the two classes are completely incompatible. The Valor Bard is completely incompatible thematically along with all the smuggled in, unable to be detached/traded out, arcane magic (and most of the spell types to boot).
A pinch of the Battlemaster, a smidge of the Purple Dragon Knight, a dose of the Mastermind, and a helping of the Valor Bard...all torn apart and put a mechanically and thematically coherent and functional base chassis. That would be the equivalent of what you have available to play a classic D&D Ninja in 5e.
There is just no comparison. You're not a better guy than Warlord fans for putting stoically enduring your lack of Ninja. Because you don't have to do so. Because its there. And it isn't just there, it is better in every way than the classic (really not so good in play) AD&D Ninja.