Winning isn't fun.
Losing isn't fun.
Fun is what happens prior to winning or losing.
Most of us are having fun regardless of the score.
The non-fun aspect comes from the chat log if you opt to not have people muted.
League of Legends is enjoyable.
Even when you're playing bad or losing, you still enjoy the game. Which is why you play another match.
Tilt doesn't happen from dying repeatedly in lane.
Tilt happens from dying repeatedly in lane, then some asshole giving you a hard time about it.
The trash talk from the enemy (opponent) doesn't bother you. It's expected and we accept it.
It's motivation and encouragement.
No, things start to get not fun when teammates decide that you are the reason that can't enjoy the game.
We've all been in the situation where we've completely stomped the enemy team.
The team KDA is like 30/2/20, you have 10 towers up, they have 0 with all 3 inhibitors down.
You ACE their team one more time 35/2/25 and when their Nexus is at 10%, your team FFs just because.
You still had fun, you still enjoyed the game, it wasn't about the win or loss.