I found exactly the discovery fulfilling in Dwarf Fortress, Rimworld and Minecraft. Once I mastered those (well, maybe it is fairer to say "once I plateaued", there are way more skilled players than me) I found much less interest in them. Sure, I still play occasionally for a bit after a big update drops, but that is pretty much it. Oh and yeah, puzzle focused games (as long as it isn't slide puzzles) are great too. I fondly remember Myst, Monkey Island and other puzzle games like that.

Some people like games where you need to grind (idle clicker games seem to be purest/insanest form of that), and that is something I don't get at all. It is just pointless busywork, just like those repetitive achievements ("kill N enemies with X style attacks") or collectables. (Achievements that are on the form "find this hidden thing" or "do this out of the box thing once" I do understand more.)

To each their own indeed.