The loss of C++ compatibility effectively removes the biggest thing that my Zig fan friends mention to me.
The loss of performance (however temporary they say) is the other piece they mention.
For casual readers, it's a proposal, not something decided
The sub-items of this task are still valuable to complete even if this overarching proposal were declined. Most of them are not being completed as a prerequisite for this proposal. There are benefits gained even without the full removal of LLVM.
I can really respect the really wide-reaching views and goals of Andrew with zig and in proposals like this, even if I don't agree.