The mod crashes if BetterNether or BetterEnd is installed.

BetterNether crash report: crash-2020-10-23_22.18.35-client.txt
BetterEnd crash report: crash-2020-10-23_22.20.23-client.txt

A user posted an issue on MoreBlocksMod issues. It crashes minecraft as it loads the client. Keep in mind that its in speculation. Thought it would help. Thanks!

tvanprooyen/mbm#2

yeah this crash has been investigated and should be fixed in the next patch

fixed with new release