it really does depend on the game and their method of communication. Games that involve matchmaking seem to be safer than server-based games, because the online interaction goes away after an hour. I'd be totally fine letting my kid play things like fortnite, splatoon, Call of Duty, etc. it's games where the server interaction lasts like world of warcraft, minecraft, and Roblox that I would be worried about.

also, no child of mine would ever have a discord account so long as they live under my roof.