This is extremely annoying, have tried removing Applied energistics, removed foamfix, used the useless bootstrapper, tried lower versions, tried this version, nothing fixes it.
Have you tried simply renaming the spongeforge file to _aspongeforge to force it to load first? It looks like librarianlib (and more) is loading mixins early.
If that fails, can you please make an issue on our GitHub repo so it can be worked on?