Same issue here, i thought i just had bad luck with RNG, found a cave, picked it clean : 1 claw, 4 furs and not a single piece of jute, didn't even see a signle cultist. Out of frusration, decided to hit every single wall to look for hidden passages, be it in the cave part or "cellar" part. Nothing
At this rate, i won't have enough moutain biomes on my map to do anything.

I was hyped about all that "Cult of the wolf" upgrade, but seing the amount of content i'd call it the "Hole in the ground" patch