Our midfield is certainly our major issue right now.
That's partly down to the players but also partly (imo) to the coaching. Based on some of the analysis we saw in the recent thread looking into our difficulties in playing out from the back, we could do more even with the limited players we have and (by extension) we could get less than we should from a midfield of better players too. But of course improving the players is easier than improving the coaching.
Given the context of the rest of our transfer window though, I would be happy to get a midfielder who can at least dislodge one of the McFred pair, even if they're not top class, or a specialist DM, or functionally dissimilar to those two.
It's important to remember that if the team is coached properly then we shouldn't need every aspect of the team to be superb. Hell, just last year City won the league having to rely on Ilkay Gundogan as their top scorer with a measly 12 goals. In reality there will never be a point where we don't think we need some signings.