There have been instances where it worsens performance. My computer is mid tier-ish at this point (3070, i7 10700k) and I haven’t noticed any poor performance from games running Denuvo (latest I tried Dead Island 2). It’s likely worse performance loss on older systems, but those older systems probably can’t run new AAA games well as it is.

I think most people don’t like the fact that it takes a while to crack games running Denuvo, so they’re not able to be pirated for that time.