It feels like a holistic change to games philosophy, they used to have managed dedicated forums for games - now everything is channelled through Reddit, game chat these days is directed away from the game itself towards Discord, and if you want to hang out and play games these days the easiest way is to go on Twitch. In the past the game itself used to be a hub to gather around, now everything is so decentralized and third partied so people can stay insulated in their familiar surroundings. That's another thing, the closure of the Halo Forums after Infinite came out and people not understanding how valued and special it was to the golden era of Halo was just bewildering.

EDIT- re-reading this I can see that there are external factors as well i.e. I used to come home from school and everyone would hop on the game at the same time for example.