There's nothing wrong with LLVM itself, my point is we could've picked a lower level model which don't need a complicated setup like LLVM. Or one that you can direct shipped optimized compiled result of LLVM, that will be a much better world
Do you have an example in mind of a lower-level instruction set that can be efficiently translated to different real-world ISAs?
Performance comes only after those two. LLVM as far as I know, has a completely different order of priorities.