[blix]

That's a pretty strong absolute, which probably means it is not true. It is possible to oversimplify things from multiple angles.

Recent work[1] has argued that microbal and fungal diversity did not play a significant role in the development of coal deposits, but rather it was a combination of environmental effects that generated swamps where anaerobic conditions prevented plant decay. These conditions still exist today, we are just actively removing them.

[1] https://www.pnas.org/content/113/9/2442