Funny, the games you don't play great but get camped for give S but the ones you play well are S-/A+

It always amazes me how I can play a game where I'm only moderately okay in lane, maybe even losing lane getting pushed in, but my lane opponent is oblivious to the map and I get a few kills off of ganks and I don't even play a good game overall and yet I get an S or S+ (e.g. my last Ahri game).

Then the game where my jungler barely visits my lane, I get ganked repeatedly, and yet I go 7/0/8 with decent CS and damage dealt to champions, and I only get an S- (my last J4 game).

I mean, clearly the mastery system doesn't care at all about lane matchups, jungler proximity, etc... S grades seems to have very little to do with actual talent (unless you're solo killing a garbage lane opponent, or are in an excellent lane matchup) and much more to do with getting a lot of jungle presence and getting fed early and snowballing.

Have had several games where I think I'm finally going to get my last mastery 7 token with an S or even S+ and end up with an S- or an A+, then turn around and have a mediocre game where I'm not expecting anything and just had a fun game and out of nowhere I get the message I have a token and got an S or S+. Really doesn't make sense to me.