The spread of "skill-based" matchmaking and ranked competitive ladders largely took away a valuable communal aspect of online multiplayer games, IMO. Getting dropped into a match with a bunch of random people you'll probably never see again just makes things so impersonal, which can cultivate a lot of toxicity.
Some of the best times I've ever had with online gaming were from finding a dedicated server with settings I liked, hanging out there often, and gradually getting to know the regulars and becoming part of a community. I've never had that kind of feeling from a game with automated matchmaking.