We have 9 players who are truly good enough to be starting for a club like United right now. 3 of them are keepers so we have just 6 outfield players (De Gea, Henderson, Romero, Pogba, Bruno, Van de Beek, Greenwood, Rashford and Martial).
Then there are a handful of players who are either good squad players (Shaw, Maguire, Lindelof, Matic, Fred, Mata) or players who can become good enough (Wan-Bissaka, Williams, Tuanzebe, McTominay).
That leaves Grant, Dalot, Smalling, Jones, Rojo, Bailly, Pereira, Lingard, James and Ighalo who aren't good enough and are unlikely to ever be.
I think we need top class options at left back, centre back, defensive midfield and right wing to be able to field a starting 11 that could realistically challenge at the top. Then, if you say Henderson, Williams, Tuanzebe, Lindelof, Shaw, Matic, Fred, McTominay, Van de Beek and Greenwood offer decent cover, we still need better cover for both wing or wide attacking positions.
We're 6 signings and 10 outgoings away from having a squad capable of mounting a title challenge.