Matewis: TF2 can be insanely fun, but it depends on the teams. It's at its best when both teams are almost evenly matched.
The good thing about TF2, compared to e.g. its predecessors (TFC and QuakeTF), is the "scramble the teams" vote, automatic balancing of the teams during the play (players may be automatically switched to the other team on the fly, if the teams become too lopsided), and the auto-scrambling between rounds. Those do really help to keep the games more even on a public server.
However, sometimes you still end up in a server you don't like (due to other players). For instance, lately there has been an influx of TF2 players who don't come to play, but hang around in the server. Their idea of fun is just to constantly dance around in the server, without anyone shooting at them or them shooting back. Heck, I've been once kicked out of a server (voted out) as I kept playing while a big part of other team members wanted to stop playing and just "party" (ie. doing nothing but dancing around with their characters).
I just hope to find the servers where people come to play and not to Facebook there. I recall reading sometime ago of Counterstrike players who were apparently some real-life pacifist activists, and tried to stop others from shooting each other in the game, hanging some virtual pacifist posters on the CS walls etc. Not sure if this about the same thing? They try to stop people from playing an online "war game" because war is baaaad?
In instances like those, I remember why I prefer single-player games. At least then I am not affected by the assholiness of the other players.