I'm not sure how far - or not - in the minority you are, but plenty of people care about 14's gameplay "at all" have have perspective "at all" and do like some or most Jobs as they are now.
1) Because the vocal minority is VERY vocal.
2) Exactly ONE ultimate has had this done at level/current content, done by an extremely skilled set of players cheesing mechanics. One could argue it's not the roles but being able to wait to accept raises that was the issue.
3) See (1)
4) They don't "feel incomplete" to everyone, they do to you. That's a subjective position, not a statement of fact.
On (4) specifically, this is where you are going to get the most divergence between players. Whenever you use the word "feel", you're talking about something specific to you. While some others may feel the same way, still other people may not feel that way at all. It's like taste in music or art etc. For example, SMN's Summons don't feel monotonous to me at all. Each one has a nice dopamine hit that I enjoy a lot. I'm not saying my position is universal, but I am saying yours is not, either. And your DRK statement there is literally you arguing for homogenization/boredom - if DRK DIDN'T have MP management and DID work like the other tanks "use their skills anytime on cooldown", that would be the dreaded homogenization demon rearing its head, would it not?
The only way to know (1) and (3) would be to see what the entire playerbase thinks. (4) is subjective and thus there's no way to prove either way. (2) is an extremely niche situation in extremely niche content that has no bearing on much of the game and was done by extremely niche/skilled players using a very specific niche strategy (Cover + Invulns + cheesing waiting to accept raises + RDM mass raising potential) and still running dozens or even hundreds of times until the RNG gods lined up for them just right. The fact people use that zero healer TOP clear as evidence of ANYthing is honestly absurd. Much less using it as some indictment on the entire game.