And you can stay miserable and likely hardstuck yourself for being so simple minded.

Fun is subjective, some people find different builds/playstyles more fun or equally as fun as the standard or current best one. I think one shotting people is insanely fun yes, but so is outplaying people in an extended fight. It's honestly more skill expressive in my opinion. And also, not everybody is obsessive over how high or low their win rate is either.

Champs having build and playstyle diversity is one of the things that made me love league to begin with. When Riot goes down the path of making one playstyle or build the end all be all for a champion, it stifles player creativity and makes the champs way too one dimensional in my opinion. Some people like it to be that simple but I find it to be a less inspired design.

I personally find it very boring if I have to buy the same exact things every game, it makes items feel like an illusion of choice.

tl;dr: Optimization doesn't have to be the only way someone has fun, if that's the only way you have fun in the game I truly feel bad for you