This already happens. This is what people like you dont get. IT ALREADY HAPPENS, we have this fucked up homogenized mess and they still cant balance their game.
This is the main reason why custom builds could never work. There are meta builds, and then there's everything else. Want to do Raids or Strikes(Trials)? Too bad, you need that meta build or you're likely not getting in the group. Trying to heal or buff without an optimal build? Get out we can get somebody better.
As much as I love GW2, I won't deny the amount of pigeonholing that the playerbase does for anything that's considered high level content. For a good example of a class that's completely pigeonholed, Druid. You are healing/supporting as a Druid, period. You will not do damage builds, you will not do anything less than optimal, and you WILL do every mechanic because only a few people need to know them and the rest of the group is too lazy to learn how to do A SIMPLE MECHANIC THAT TAKES LESS THAN 5 MINUTES TO LEARN. Sincerely, a player who was stuck in Druid jail for 4 years.
Skill trees or custom builds come up every now and again and every time it has to be said that no matter what the only build that will be acceptable is the optimal one. Doesn't matter if all of them can clear content or even perform well in the most difficult content, the community will insist on everyone following the optimal build at all times or they will be removed from parties. Even with the slight difference in performance we have with the jobs now there are some that are excluded from PF simply because they don't perform as well as others, not because they cannot clear.
If you aren't doing Savage or clearing Savage week 1-2, you shouldn't be concerned about balance in this game at all
What does it matter if a certain job is worse than another if you aren't doing that content at that level
It seems to me like a lot of these complaints are things that have been in the game since time immemorial. Not saying these are things that do not need addressing or could use a shake up, but I do not know why people suddenly think the game is as good as dead because of it.
Because for some reason it's currently "hip" to be a doomer and they're all trying to change the game into what they imagine it should be. If I didn't know this was the FFXIV forums, I could have sworn I walked into GW2's subreddit pre-EoD (imagine this in a full subreddit where you get downvoted for saying ANYTHING good about the game).