Assuming your assessments are correct, they are still immaterial.
He's not playing forward, so it doesn't matter if he's better than James, Martial or Rashford. Mata hasn't been in the squad for months; being better than him might get you on the bench and not on the field. DvdB hasn't been on the field much since he arrived; being better than him might still keep you on the bench and not on the field.
Except for their game against Leicester, he's played the same position in a 4-2-3-1 as Bruno. That's the only positionally comparable player in our lineup, but you don't mention him.
Truth is, he's good enough for a backup to Bruno. Truth also is, he doesn't want to be a backup. It's just better for both sides that we get a good deal for him to move on.
Oh, and Lukaku wasn't good enough, Pogba wants to leave (then he doesn't, then he does, then he doesn't, then we just get tired of the drama), and DDG has been on a statistical decline to mid-league for the last three years (as shown in other threads) while we have possibly the best up-and-coming keeper in the league supplanting him.