Unless I'm mistaken, Denuvo constantly encrypts and decrypts everything in the process' memory, including executable code, in order to conceal it. There is no way to do that without massive performance overhead.
There are uncracked Denuvo games to this day that don't have performance issues. Not everyone is incompetent in implementing it. That doesn't mean I'm defending it (but Reddit/Lemmy will like to take any sort of non-attack as defense sooooo), I'm just saying that there are Denuvo games that don't suffer performance issues.