Bosses. Big ones. Mobs that do serious terrain damage and require grappling and building to defeat. Shadow of the colossus stuff. Maybe make it so you have to build a totem with a certain design and rare materials to summon one, or they could be random spawns. Or make a sacrifice at an altar- turtle bones, diamond dust and essence of water lv3 to summon a medium water turtle god.
It should be possible to fail some raids. Boundless meteors was too easy.
Legendary unique drops.
Puzzles and generated dungeons. Even if there’s only 10 basic cube shaped room designs, with different colors and randomized layouts including dead ends, you could do a lot. I would enjoy Zelda style puzzles. Maybe also stuff like The Witness. There could be agility puzzles (walls and ceilings that are ungrapple-able) and timed courses (press a button that opens a door for 60 seconds etc)
Perhaps Endless dungeons for Farming where you can place cheasts or Something and RECLAIM IT or instead make 1 chest at each Floor of the Dungeon to Put your stuff in Like in Path of Exile in some Dungeons