So is this even actually a real problem in real life or is this just one of these internet things? How many of you have had your must-have character idea denied by the GM? How many of you have had players insist to make characters totally incompatible with the pitch? Because I can't really recall either of those having happened to me in real life... There may have been some discussions about could this or that work, but I really cannot remember any actual serious disagreements. I mean I have played for decades, so it is possible that something like that has happened at some point and I've just forgotten, but in my experience this doesn't really seem like a common problem.
I think the problem is a bit exaggerated. However there are some really bad players and DMs out there.
But really I think the real drive of the discussion is: Really Narrow Settings.
I've seen some really narrow setting write-ups and race/class restriction in books, games, and forums that limit PC options so hard that you are just begging from the bumping of heads at Session 0 or players insisting on roleplaying the craziest characters as their creative juices were stifled on on the character sheet.
That's why I'd almost never run a human only campaign again. All the PCs are bores or loons with nothing in between.