Had an issue on our Direwolf20 server with undergarden generation so I thought maybe its just our current world or something that was causing the issue so I downloaded a fresh copy of the server of Direwolf20 1.16 1-6-1 and created a portal to the Undergarden. It looks exactly the same as it did on our current server. There are mobs and regular terrain. But I don't see any growth, no ore at all. Here are 2 examples. Based on videos I have seen this isn't how its supposed to look.
I've found catacombs that contain chests and mobs but other than that its just blocks, no vines, no vegetation at all.

Yes it does, and I apologize because I think this might not be the right place to post originally. I guess I could try removing the immersive engineering and see if that makes it work?

I tested out just the mod on single player and server and its fine. I also posted the issue to the direwolf20 github as well because I wasn't entirely sure what the issue was.

does the Direwolf pack contain Immersive Engineering?

One player of my modpack also found this conflict (spoiler modlist: https://www.curseforge.com/minecraft/modpacks/magica-infinitum-iii).
Shorepion/Magica-Infinitum#9
I made a new world with worldtype "default" and it seemed to fix it. My guess is that there is a conflict with Biomes O' Plenty since its the default worldtype in my modpack.

I'm getting this issue on both default and quark:realistic worldtypes. Neither Apotheosis nor Immersive Engineering are installed, though Psipherals is. Here's the modlist: https://paste.gg/p/anonymous/94df3a21c5e64b68bb7ed636a2154b94

I'm on singleplayer, by the way.