It's not inferior to 2020 for so many reasons (better "ball awareness" above all), but yeah the referees are hardly a strength point of this game.
I've got a penalty called against because one of my AI-controlled players stumbled into an opponent, and I got nothing when my forward got elbowed in the face in their box.
Plus, as it's already been said, I've seen some fouls being "reversed": the CPU player fouls me, I hit him while falling, the ref calls the foul against me.
It also happened in my favour, but very rarely.
Other than that, I find it more refined than 2020 and I'd pick 2021 over 2020 at the moment (not that the vanilla 2020 had perfect referees, after all).