fraglandsin pubs, offclasses aren't anywhere near as useless as they are in 6s.
So that little snippet is really the long and short of what you wrote. Problem is, pubs aren't competitive. I don't mean that like "pub TF2 is different from comp TF2," I mean that pubs do not foster a competitive mindset. They don't reward playing competitively. Pubs are random, and trying to apply anything you learn in a pub to competitive makes no sense. Pubs are chaos mode. There's no way to keep track of 23 other people; there's no telling what you're walking into or getting your team to follow you, there are random crits and all sorts of other dumb mechanics. Literally every weapon in the game--even the sun on a stick--will find its time to shine in a pub. If you find that fun, fine, you do you. But don't come talking about how any of that makes sense for a competitive environment. It just doesn't.