why doesn't Riot ban nonverbal toxic players?

There is a dude that locks in Vayne top and just farms... whole game all she did, ended 2-0-1 in a 40 minute game on a 42 kill team we went top to fight with her she recalled went bot, same if we rotated toward her way... all she did was rotate and farm. let her lane opponent free farm had 4k damage all game because she only attacked if she was attacked all we did was ask her why she auto locked Vayne in pregame and how we dont think thats helpful to our comp and then rest of game she talked about how she was going to afk because we disliked her pick and how she"didn't care if we won or lost because I have multiple accounts" even saying he will refuse to help us But because he had great farm because that's all she did for 40 minutes...and they weren't afk or shit talking, Riot is fine with this since they can claim its off meta or something. its not fair that for the long time this game has been out they have been allowing this without a ban on these guys accounts... its stupid how we have to do and safely tiptoe all these toxic players or if we call them out for being a toxic player we get banned