A theory of everything would at best unify gravity, the electro-weak, electro-strong, and electro-magnetic forces. It would not explain most of the fine-tuning.1
Our best evidence suggest there just is no such grand unified theory.1
M-theory fixes the fine-tuning parameters.
But no, M-theory is especially unhelpful.
• [No such theory exists](/universe/fine-tuning/by-theory of-everything#none).
• It is entirely unknown whether it would eliminate even the few instances of fine-tuning it hopes to explain.1