Is it not also possible that people have found "better" ways to pirate and are not, therefore, directly visiting the sites.
My personal usage it's most definitely up in the last 12 months but I've never actively searched for anything directly and I don't torrent.
Maybe it's just old school piracy that is down.
It's an android only apk which you sideload and strips all adds from YouTube content.
I've long said to myself, the day revanced, smarttube and adblockers stop working is the day I stop browsing YT.
I watched my son showing me something the other day, he can't yet login via revanced so still has ads, what a shit show.
I asked him how he copes with all the ads, he said I'm dumb to them now I just ignore it. But still coming from zero ads to that was a very jarring experience.
Unfortunately that's very true especially regarding TV Shows.