Loading MixinBooter 8.0 and above with CubicWorldGen 0.0.85.0 and above makes it crash immediately after hitting play within the Minecraft launcher with exit code 1.
Here's the log:
https://gist.github.com/vainlaind4in/d84dcafa2ed9b292094da9037f45b644
I have been told that it was fixed by this commit but it wasn't implemented into the CurseForge version.