Mostly endless, quite possibly story-less games. Played this sort of stuff a lot more in the past, nowadays either when I'm too tired for anything else, or I'm on a playthrough.
Some cool endless games I can personally recommend include:
Deep Rock Galactic
Cataclysm: Dark Days Ahead
Trackmania (only played the 2020 version)
Monster Hunter (playthrough-friendly, only played 4U so far)
Animal Crossing (playthrough-friendly, only played New Leaf)
ArmA 3
Left 4 Dead (2) (playthrough-friendly)
(maybe in 5-10 years when it will be more complete) Helldivers 2
Space Station 13
Club Penguin
Bloons TD 6
Stardew Valley