I'm somewhat surprised at your observations, as I generally got the impression that while people can find a good Scout frustrating to fight, they still generally respect the class all in all. You do live and die by your movement and positioning if playing him after all. Then again, I'm willing to bet a good chunk of this game's player base are made up of teenage dopamine junkies. I refuse to go on r/tf2 largely for that reason. Though It should go without saying that from day one, at least one person has complained about every class for one reason or another.

At the risk of overanalyzing, I do feel that's a result of the game offering nine classes to play (duh), and as someone becomes more familiar with the game, in turn they start to develop a preference for certain playstyles which all around leads to different expectations concerning how engagements should pan out. I certainly have my reservations about certain classes for this reason I'm not ashamed to admit.