His ability is absolutely in question. This is a guy who Southgate consistently played for England despite him rarely performing and there being far better options. His performances for us, when fit, have simply mirrored those matches, with him struggling to do anything productive on the ball.
He's obviously not a bad player, and he’s fine as a squad player (Lingard/Sancho type level), but we are paying him far too much for that role. He’s quite some way off the standard we should expect of a starting number 10 at United.
We are stuck with him though, as there’s no way any other club will take him off our hands given his injury record/ability level. Just have to hope that he can do something in the next 3 years to justify the £100m+ invested in him.