Ancient Debris generating more sparsely than normal in the latest 1.17 snapshot version. (After comparing seeds between versions, it seems that there is no bug.)

Put the summary of the bug you're having here

What I expected to happen was...:
Ancient Debris to generate as normal

What actually happened was...:
Ancient Debris did not appear to generate as normal

Steps to Reproduce:
1. Generate a world in this snapshot and search for Debris in the nether.

2. Use /fill to remove netherrack (although I observed this through survival game play, after mining normally at y=15 for a significant amount of time and finding 0 debris)