Is it a 1-vs-1 or co-operative game with only two or few players, or are there lots of players in teams?

At least in team games like Team Fortress 2, I couldn't care less if someone is raging, as long as he is not shouting to the microphone. If he is, I can either mute him, or start a vote in order to kick him out of the game. Problem solved. Maybe your game doesn't have those options?

Sometimes people seem to rage for seemingly valid(?) reasons though, sometimes not. Like if most of the team seems to be just dicking around and not really playing. I guess that is their prerogative, but it also makes rest of the team's game futile when only a small part of the team is even trying. One can try to vote such idlers out too.

It is obvious you can't please everyone. I am baffled by e.g. people who rage because someone is making flag captures in Team Fotress 2 (apparently they'd rather play the game as a team deathmatch game instead with no capturing of flags etc.; I say they should be playing some other game then), and sometimes some rage that someone should be kicked because he plays too good, and is destroying the fun for him/others.

Like the other day, there were a couple of enemy engineers in Team Fortress 2 which were extremely masterful in preventing us even leaving our base. They had found pretty much perfect places for their sentry guns, kept repairing them and successfully harassing anyone who tried to destroy the sentry guns, even foreseeing if they were trying to take a longer detour to them. And the rest of the enemy team was supporting them beautifully, harassing those who tried to destroy the sentry guns or fight the engineers.

I think there were lots of rage quits and some cried those engineers are destroying all the fun for the losing team, but the only people I personally was slightly mad at were the incompetent team mates who wouldn't simply change their class to a more suitable one to take care of the sentry gun problem. A hwguy+medic combo, anyone? Why do you insist playing as a sniper or a scout if you can't even exit your base as one?

I quickly changed to a soldier with a precision rocket launcher in order to get the sentries, trying different routes to them etc. It took awhile but in the end I was able to distrupt their engineering operations enough, and trying to make sure they don't come back.

I have nothing bad to say to those couple of guys, and their supporting team, controlling us like that. They did fine, we had a problem as a team.

That's the unfortunate thing about TF2. It can be a heck of a lot of fun, but it strongly depends on what's going on in the two teams, unlike a free-for-all type of game like Unreal Tournament.
TF2 I found is at its most fun when the two teams are more or less equal in skill, or at least when one team isn't totally dominating the other. And sadly this is often not the case, like when you're stuck in a team where nobody wants to be the medic, much less do the medic-heavy combo like you mentioned.

I used to love those matches where there was a tacit understanding of the basic tactics used in TF2, as opposed to those games where everyone just stormed off on their own to get slaughtered :P

My experience with WoW was almost the opposite to that, instead no-one ever talks to each other even when in a dungeon.

It's about costs. About the only way to make sure you get a community that fits most people that aren't trolls or people with temperament problems is to moderate it. As in real people watching over chat and play behaviour.
Yeah you can use automated functions or community moderators but that will never work that well. The game companies will never have moderator employees enough to make a real difference because they can't afford it or won't have it cut their profit.

What you see is essentially the real human race. Human behaviour when you run no risk of having to deal with consequences of your behaviour. Lovely isn't it?

I used to play MP games in my youth. A lot, actually. But times changed and most of the online communities are downright toxic. That's also the reason of why i am avoiding MMO games passionately. So i stick to SP games or at worst Co-Op games with selected friends (if there is an option for that).

Damn. I miss my old LAN parties, when i had a ton of people around and had a lot of fun, no matter if we win or lose.

LAN parties. That's something I miss very much. :/

I think the change is because of competition. My memory is foggy about this but I have a feeling that the more competitive multiplayer gets the more toxic it become. Nowadays it seems competition is like the be all and end all of multiplayer.
Haven't really looked into it but that's the feeling I have.

Yeah... but on the other hand I take it as a challenge, trying to distrupt their streak and turn the tide. Either I change to a soldier class and go apeshit on everyone killing as fast as possible, or something. But there is only so much one person can do if rest of the team is afraid to leave their base but just dick around the home entrance all the time, and flee back to their ammo room when they get even slight damage. Cowards! So what if you die, you'll respawn later.

Nothing gives me a greater pleasure than being able to slip by the dominating team as an engineer, and unnoticed build a sentry gun behind their backs, just as they are about to capture the flag. Suddenly their total dominance and certain victory is turned into a pile of bodies. :) Or, while the enemy hwguys are ravaging your base (and forgetting to defend their own, thinking no one could have possibly get out of the base alive), making a few quick flag captures with a scout.

I used to play Counter Strike a lot (probably 15 years ago now) and the community was hit and miss... most people were fine but some were assholes. I mainly quit because of the changes to the game rather than the atmosphere of the community (though I don't think I could get into a mutliplayer game these days knowing how bad most communities are now)

Best multiplayer is big LAN games, we used to go to a cybercafe where they did big LAN CS games. Nothing quite like 20 - 30 people sitting in a dark room kicking each other's asses.

To the original question:

I quit Quake Team Fortress because the community started to be full of cheaters using hacks, and not even trying to hide it. Luckily there was Team Fortress Classic to jump to at that point.

I quit Team Fortress Classic because of the meager community, as most had moved to TF2. Playing against bots was never my thing.

Engineering class was my favorite :) It's weird how much satisfaction there is to be gained from your teammates heavy reliance on one of your teleporters. But nothing, absolutely nothing beats the euphoric relief you get from wasting a spy that that's nosing around your turret and dispenser, especially one who's trying his best to act like one of your teammates.