You're right, it isn't about Smash Bros. It's about you complaining that your computer has an issue running League. So does mine, but you don't see me bitching about it. Using Smash Bros as a reference, however, brings up the small point that you aren't considering that a game that looks as good as Smash Bros, however simple the art style may seem, is actually taking quite a bit more power to render out than you seem to believe it does. It looks cartoony but it isn't.
There is a solution. You put the game on low settings. This might come as somewhat of a surprise to you, unless you computer is upwards of 5 years old, chance are that it can run League of Legends just fine. There are very few computers that can't. It's why saying "I can run League of Legends on high settings" isn't something to brag about because, all in all, it doesn't actually take that much to accomplish. I play with it on low settings and even though my crappy laptop has issues with overheating if I try to play anything else, and I can run Diablo III on low settings at a whopping framerate of 20 fps, I can run League at 60 fps provided that I keep my settings low.
The graphics do get dumbed down if you turn down the video quality. Put an image of a champion set to very low, and a champion set to very high, and you can actually see a pretty pronounced difference in how the two of them appear.
There is an alternate graphics setting. It's called "very low."
You aren't saying they need to replace all of them, no, but what you're saying is probably worse. You want them to rebuild an entire game around these sorts of cartoony graphics but you clearly have NO idea what all that entails. You're asking to have two separate sets of models for the exact same skins for every single champion in the game. You're asking to double the size of the game on player's drives, and you're asking them to make alternate models for every champion that also retain the exact same proportions and hit boxes.
You're asking them to essentially design an entire game all over for your, or whoever else who can't run it on high's, benefit.
I am giving you constructive advice. Just because it isn't what you want to hear doesn't mean that I'm being overly negative or trying to bash on you. I understand the point that you're trying to make perfectly well, but as someone who's actually studying game design currently I also seem to have a much better view of the entire process it would take to accomplish something like this, and it's no small undertaking. In most ways it's actually just flat out impossible to do.
Are you going to ask Diablo III to be more cartoony so you can play that?
What about Final Fantasy XIV?
Or possibly Titanfall?
From the way you're talking it should be simple to make a game appear to have that cartoony "timeless" style.
I'm very sorry, but it isn't. Turn your settings on very low like the rest of us that don't have super recent computer models or rigs that we've built ourselves, and stop putting your hand towards Riot and expecting them to placate to you just because you don't like that you can't run the game the way you'd like to. It isn't Riot's job to make an entirely different set of character and environment models to cater to people with shit computers like us, it's their job to make a standard set of graphics that have a sliding scale based on performance versus quality, and to try and optimize it as best as they can. In that regard, Riot's done their job just fine. They've picked a design theme for how they want their game to look, and all we can do is accept that.
You're QQing because your computer sucks, and no amount of alternative models for champions based on graphics settings is going to change that. They could make it whatever style that they wanted and it still wouldn't help you computer run it on a higher setting.