I have never, ever seen anyone say "I don't want to play a T4 class because they're too weak." I have never, ever seen anyone say "You're bringing a T5 class to the game? You're worthless." I have seen people say "Dude, that's a pretty big tier difference we're looking at. Are you sure you're going to be cool with that?" And if they're not cool with that, we work together to make the party harmonize without hurting anyone's character concept. (If they are cool with it, they aren't surprised when other people sometimes get the spotlight, because they knew going in that a Crusader does a Knight's job better.) I have seen people say "wait, my Psion's going to be the only T2 in a bunch of T4/T5s? You know, maybe I'd have more fun bringing in that Rogue build I've had in my head for a while." And then they do.
The plural of anecdote is not data, as the saying goes. But my experiences are just as valuable as yours, and I think that what you're saying here is, at best, a highly skewed representation of how it goes for many, many people. In fact, in my experience, lack of understanding of the tier system is a far, FAR greater source of GM stress, player stress, and group disharmony than ANY discussion of how the tier system actually works. I'd also argue that you're missing a lot of the point of what JaronK's actually saying, but I'll let someone else handle that.