Loading MixinBooter 9.1 with CubicWorldGen 0.0.152.0 makes it crash immediately after hitting play within the Minecraft launcher with exit code 1.
Tried loading slightly earlier versions of both mods, doesn't work to mitigate anything.
Here's the log:
https://gist.github.com/vainlaind4in/d84dcafa2ed9b292094da9037f45b644

Will there be a fix to the main version?

You will have to ask the mod author where they published the later version.

Update CubicWorldGen to newer version

CubicWorldGen 0.0.152.0 is the most recent version I can find on the CurseForge page, and that still crashes.
I updated the log which includes the most recent version of the mod, although I don't think there's anything different.

After testing a little more, I found out that MixinBooter 8.0 and above versions crash but 7.1 doesn't.

They fixed the issue by this commit, but seem like it didn't on CF for some reason