Mount and Hojlund have been good signings and are a fit for any team that wants to control the game with and without the ball. Onana is also is a fit for a more attack minded team, especially in possession. Unfortunately for him his form has dipped in recent weeks but the signing itself made sense if the intention was to play a more expansive game. Antony's price was way too much, but the actual player himself was a fit for a possession based team that played in a compact high block and expected the players to provide the intelligence and intensity out of possession which is a requirement.
United's bigger problem is the players that have predated the aforementioned players above. And those players have a bearing on our playstyle in the final third and defensive third, and the manager seems to be playing around the weaknesses of those players whether that be in possession or out of possession. Then there's CBs still at the club who always lacked the physical and athletic capabilities to succeed in a EPL that is being dominated by teams who evade/resist the opponent's pressure, defend transitions in a higher line whilst also being a big threat in transition themselves, as well as having a strong defensive rest phase where they can slow the game down and utilise their off the ball movement to create numerical superiorities.