By the way, Manchester United has really talented players like Garnacho, Mainoo, Amad Diallo and more. One of their focuses should be the development of these players.
All of these players have a big potential to tell the truth. They shouldn't be wasted. They will be the future of this team. I like this side of this team as well. I always see really skilled young lads waiting for their turn to show their skills. They never fail too. Especially Garnacho - Mainoo are doing great recently.

Big teams would be after them shortly.
Would you ever want these players to be sold at this young age?

My answer will be, never!
If I were Manchester United management, I would not sell this young boys unless there is very much exorbitant price offered for them which will assure me that I can buy other good talents like them. But also we need to understand that having young players Is tot enough without experience players to guide them. A team that is composed of majority of young players will not be mature and will not be able to win trophies. They can play well throughout the season but at the end of the day no tangible tangible trophy because of inexperience. It is nice that when you have young players, you keep them under the mentorship of old and experienced players and allow them to grow. If someone like Cristiano Ronaldo is still in Manchester United, Garnacho would have developed faster than this because he will be happy playing alongside his idol.
Take Real Madrid for instance, they had a lot of young stars and talent to pilot the affairs of the club, yet the kept pleading with Toni kroos and the Modric to remain and the groom the young ones. So, I expect Manchester United to buy experienced players to compliment the efforts of the young ones.