Holy shit, you just made me think about it. In the last 25 years we've only signed one midfielder who was an unmitigated success (Carrick).
Obviously we had Scholes, Butt, Fletcher and Giggs (for 1-2 seasons) who came through our youth ranks, but still. Every other midfielder that we've actually bought over the last quarter of a century either failed or at best were very inconsistent. Hell, Pogba is probably our next most consistent and he's been mostly 50/50.
That's an incredible statistic at any time, but especially when we've had the most successful period in our clubs history during that time. Signing midfielders certainly hasn't been our strong point.