I agree with you that feats you can't collect are clutter and encourage bad feelings on the part of players.
The problem for us is that I think that CG is hoping to encourage bad feelings among players with the goal of them hating staring at those feats so much that we'll pay to unlock them.
I am not the best person to comment on the psychology of generating $1B from a game's players. While people consistently point out how horrible this approach to the game is, CG keeps making money and the servers stay lit. So maybe it does generate more revenue than it loses?
I can't say that it's a bad money decision. But I can say it's a terrible game decision in that anything that makes a game less fun tends to ruin the point of playing. We're not here because we have to be.
And while not everyone pays (and not everyone has to pay), it's crucial for game health to have a pool of FtP participants. If no one is FtP, then paying doesn't get you any advantage, because everyone else is paying too. And if paying doesn't buy you an advantage, then why pay?
Therefore there need to be people like me who make positive contributions to the community other than spending $$ (I did give some back when I first started, but I prefer purchase games not subscription games and gave them what I thought it would be worth to me to buy a game like this, then stopped spending forever). Their work, then, has to be a balance between the things that psychologically prime spenders to spend and the things that psychologically prime FTP to feel bad and thus stop playing.
To be perfectly honest, the people who are going to quit from this update are very unlikely to comment here. They play because it's fun and quit when it stops being fun without much worry about "investment". We'll never know why they stopped, really. (Not most of them.) We have to take a best guess at what will really cause people to leave, based on how those of us feel who play primarily because of the fun of the game, but are also invested in the game for whatever reason and thus stick around longer than short term problems last. For me it's the people in my guild and Discord's 50 Shards. We help each other, and even when the game feels terrible, I don't want to lose touch with those people.
So far all the worst things have expired (or I've stopped caring) before it was enough to drive me away from my friends. So I can -- having stuck through bad things -- fairly comment on those things that make the game less fun, but I can't be certain that these are the exact reasons that others' left.
Personally I hate the UI with the fire of a thousand suns because of the relentless, non-stop popup windows that hide useful information. But I don't hate everything about this update. I'll need a couple more weeks to decide how I really feel. And, honestly, with the cluttered UI and constant popups, I might not even know how I feel about the rest of it until those things are gone, because they are so obtrusive and problematic.