It just depends on how you have fun. My definition of "fun" changes every moment, depending on my mood. Some days, when I want to feel good about myself, I hop on my main, Yi and play for KDA. When I end up feeding or the game goes bad, it's not "fun" anymore for me. But usually I'm decent, so even if I lose the game, I get to kill people, so I'm still happy.
Sometimes, I just want to meme, I pick Jarvan with Aery and build AP, trying to stack up "swag flag kills". I normally lose, but I get to have fun for a bit during the early parts of the game when I do get those. It's especially more fun if my ADC messes around with me, it's normal blind pick after all. When they flame me and leave me alone to solo bot lane, it's no longer "fun" for me. Or just a pick that I have 0 idea how to play even after nearly 30 games (Kayn) but I just like playing. When I get to play that champ, I'm having fun, even when I feed.
Back in the old days, I was a tryhard, so watching the elo (it was a number back then) increase was my "fun". Losing and watching that number drop made it not "fun".
Of all the 3, the first is somewhat controllable (if you're at least decent on mechanics, you will get kills on Yi in most cases - but bad macro may still lose you the game). This goes with a lot of situations where the complaints "I won lane but lost the game" come from, but as long as I won lane, I am usually happy enough. 2nd is all about perspective, which is 100% on you as well, if you feel like you're having fun, you won't mind doing badly. 3 however, is what most people describe about their "fun", which is where all the frustration comes from because you obviously cannot control your win/loss (or else everyone would have 100% win rate which is statistically impossible anyway), so you feel frustrated that you can't have your fun of gaining elo.
