Corporation tax does need to be reformed. The solution is that rules need to be changed so very large multinational companies are taxed where they get their revenue, this means they will pay tax to many different countries simultaneously. It will mean virtually no profits will be taxed in tax havens.
This would be a huge change as effectively all rich countries would have to agree to it simultaneously, and all their tax treaties with each other would have to be rewritten.
Apparently Trump has a corporation tax reform policy that won't achieve his objective, as the problem he wants to solve is imaginary, but as a side effect it would require a reform like above to Corporation tax, so it would be good if he managed to implement his reform. (I know that sounds weird, just repeating something I read in Financial Times a while ago.)