One recent genre is auto-battlers from Dota 2 custom game tools. To my eyes that’s been the only large genre grown from in game tools in a decade which has life beyond original game itself.
Tower defenses and AoS/Dota/ARPG/Mobas as examples of the above from 90s and early 2000s. Maybe “gliding” is a genre too from counterstrike now seen outside in games like trackmania, and probably Gary’s mod is it’s own genre too. Then only genres and modes which live within the original games since (though amazing and well done).
I really think Blizzard had an opportunity with StarCraft 2 to rewrite gaming history if it’s modding tools were up to par. Instead we got custom games less sophisticated than ones 20 years younger from it. I don’t think the modding community ever really recovered being left empty handed in that era. Maybe it’s recovered, modders were left without adequate tools for a while. Modders really did produce hundred million to billion dollar genres in the past, I’m not sure if that is still happening.