I love reading r/tf2 threads about competitive play and one of the big topics is weapon bans. From what i've seen, once there's been a back and forth on the matter, most pubbers don't have much of an issue with weapon bans themselves, but using them to enforce the cookie cutter class line up. Their vision for competitive tf2 is a game where people constantly switch classes and weapons to counterpick each other for 30 minutes, which is the last thing the current community wants. To some extent, this is just a difference in taste, but I also think that the way you see "what tf2 is about" changes as you get better at it. casuals tend to view tf2 as a big game of RPS, whereas at high skill levels those class/counter class relationships usually seem much softer, and that how your team plays is often more important than what your team consists of. in competitive play, the best way to deal with a heavy is focus fire, but in pubs you switch to spy or sniper.
I'm not sure of how to solve this aspect of the divide, but I think having more high quality class tutorials aimed at pubbers would help raise the overall skill level of those who are at least somewhat interested in playing the game to get better at it. There are tons of bad scout guides out there in particular that say double jumping vs soldiers is bad and that if you aren't at point blank you should use the pistol.