The numbers don't lie:
Garnacho = 30 games, 4 goals, 1 assistNo matter how many seasons he stays at Manchester United, he won't be able to score a very high number of goals. That's why it's better for Manchester United to sell him and sell other players who are underperforming and sign players who will perform well, like Victor Osimhen for example.
Rio Ferdinand:"If I am Man United, Victor Osimhen comes to Man United next year," he explained. "I am making it happen and the caveat to that is that if I am advising Garnacho, I am telling him to go to Napoli.
source: https://www.manchestereveningnews.co.uk/sport/football/transfer-news/rio-ferdinand-makes-victor-osimhen-31373397Manchester United need good results immediately, that's why they need to sign players who will easily adapt to the team and bring good results early
These are the numbers at United. To be fair, it would be fair to compare the numbers at United and outside United. For example, Anthony has improved in numbers and overall since leaving United. Can you name anyone who came to United in the post-Ferguson era and has improved? There were probably some, but basically United is a graveyard of talent, I think that Garnacho really should leave and maybe he will progress in another club, he has potential.