I don't think there is any strategic or social value to the in-game text chat, and that Riot should consider removing it.
Overwhelmingly, my experience of the in-game text chat is negative. It is predominantly used by players to verbally abuse other players, blame other players, order around other players, or otherwise express negative feelings about the game or their teammates.
Occasionally, a player uses chat to say something nice, or communicate useful information. I'm absolutely willing to sacrifice these infrequent instances of positivity, if I also no longer have to watch human beings tell other human beings to kill themselves, throw slurs at one another, and generally degrade each other and themselves in the process. Even when it isn't targetting me, it is disheartening to see people who likely have a lot in common be so thoughtlessly harmful to one another.
League now has pings, emotes and other ways to communicate with teammates, chat is no longer a necessary feature for communicating key in-game information. Teams who want to communicate can use Discord or another tool of that kind. Chat is obsolete and is more harmful to the game than it is good. Riot should consider removing it.