Well, you can start looking at mods, there are some filler mods that populate the empty biomes up and add a bunch of bosses.

Vanilla, ya, its dead.

There's also a mod that increases the whole raid your base aspect into sort of a tower defense thing (because it can get so intense), which is way better than the biome populations imo. But both are really good.

Devs of the game wise tho? Ya not so much. Better trust in mod community at nexus than checking for new things here.