Best Online Games for 30–120 Minute Play Sessions?

Hello! Lately I haven’t had much time to sit down at my PC, so I’m looking for some PvP or online games that I can jump into for 30 minutes to an hour and still have a great time without spending days to simply learn the game. I can’t dedicate dozens of hours a week anymore, but I still get the urge to play something occasionally. Right now I’m playing Chivalry 2 and Arc Raiders, though Arc Raiders feels a bit overwhelming with all the crafting — I wish it was a bit simpler.