The MyM update killed it for me. Even before the bot invasion, after matchmaking became a thing, nearly all community servers inexplicably turned into 24/7 2fortbinebowltowerorange pub garbage or servers with dumb custom gamemodes.Seeing this game degenerate in real time was heartbreaking.
Back before all the class updates and free weekends you actually had a healthy but fairly small and insulated community, everyone knew each other and fun times were had. Then the first free weekend arrived and with it the bane of all communities: the 12 year olds. Kids screaming into bottom shelf mics and griefing when things didn't go their way.
Then the class updates started rolling around with gimmick weapons and while the Kritzkrieg was a fine addition everyone lost their mind when the pyro got the Backburner. But even that was okay, compared to the truckload of hats/weapons/whatever that came out each month with every big release game, "Buy this game and get X for TF2." And when the game finally went free those who actually bought it back then got a free hat, thanks gaben.
The game also got progressively worse performance-wise as time went on, not only effects got removed they somehow slowly degraded the average frame rate, not to mention there were weapons that,when they came out, could crash the server because they had so many particles the Tower of Ducttape could not handle it, oh and naturally every major update screwed up the spy backstab hitbox.
I don't know what game got whored out as much as TF2. I don't play a lot of Dota2 but i know its full of "cosmetics" too, but then again it's also a Valve game.
There isn't any middle ground anymore. You either play a wacky meme match that's barely anything like TF2, or a srs business comp-lite match on the same entry level maps you can find in 3 seconds via the server browser. You can't just have a regular comfy match on something like cp_granary or pl_cactuscanyon with sprays and alltalk.