Little monster variety?

So I have been playing for a bit and I have gotten a net worth of over 81000 (i assure you I didn’t cheat in any way, I trimballes w/ geomancer and you get a ton of hearthbud seeds to sell and take the hearth that gives net worth off of gold) but I only ever get goblins and orcs after a certain point. This is vey bad because I need to get the dusty tomes and there are no longer crypts or giant zombies spawning. Can you please explain how to fix this?
TL;DR there are no crypts or giant zombies spawning and I need them for the dusty tomes