I don't understand why some people think Riot balances the game around proplay
They clearly don't. Meta in proplay is pretty much always set in stone and revolves around a small champion pool of the most busted champions in the meta. A lot of picks are intentionally garbage in high elo to proplay so that they don't abuse low elo (Garen, Master Yi to name a few). Now maybe Riot did the huge mistake of nerfing some champions that were 100% godlike tier pick or ban and had retarded winrate in pro play while completely warping the metagame around their kit but that's fine cause they got sub 50% wr in soloQ? Please. Riot's torn apart because they wanna please everyone but that isn't quite working in balance terms. Other games (like Dota2) have immensely more diversity in competitive because they don't care about winrate in casual play (and seeing that, casual players play whatever they feel like and don't feel forced to sheep the prometa).