Manchester United's forwards, midfield and defense are all very weak. So I see no reason to think that Casemiro in the team will actually strengthen every position of Manchester United. Casemiro is an experienced player. But in the 2021–22 La Liga season, he scored just one goal and 3 assists in 32 appearances. So I don't think United will be strengthened by Casemiro.
Rating Casemiro performance based on the number of goals and assists might not be accurate. A defensive midfielder should be assessed based on the number of successful tackles, ball won, distance covered and number of blocks. The player is fast and physically strong, hence he is a very good asset to the Manchester United team. Real Madrid is selling him because the really need the money and because they already have a replacement for him (Asier Illarramendi). Manchester United are just waking up from their long sleep.
I'm not considering Casemiro's ability with only goals and assists. I'm just pointing out that with the arrival of Casemiro, many people are thinking that Manchester United's overall gameplay will change. I do not agree with this idea. Casemiro's arrival will definitely strengthen Manchester United's midfield. But their poor defense will not change. At the same time, until Ronaldo returns to form, United's forwards will also be weak and will struggle to score.
Manchester united need to find a solution to their defence instead of bringing more midelfilders because they already have many good players there... Ronaldo is leaving the worst days in his career as a player and i don't really know how the player will manage to exit from this situation