Manchester United is famous as a club that often makes star players their main transfer targets, so they often let young talents go to other teams, currently there are several young players in the Manchester United squad, so it seems that they are starting to try to develop young talent in the team, many English league clubs seem now to be starting to trust young squads to fill their squad to compete next season, Chelsea have been the most visible this season in trying to build their squad full of young players, so I think, Manchester United should also be able to follow Chelsea lead in order to build a squad that does have long-term prospects later.
Manchester United has often sold their young players, but in the last two seasons it seems that they are trying to start trusting academy players to get into the first squad, in addition to the players you mentioned, actually Manchester United has a lot of talented young players in their squad at the moment such as Greenwood, Omari Forson, Brandon Williams and also Hannibal Mejbri, so I think if they can be retained and given the opportunity to continue to develop in the main squad, of course, Manchester United no longer needs to spend a lot of money to recruit other players in the future.
United not only raises their own stars, but could find stars around the world and pay them good money to attract talent. The problem that they have right now is that they are spending way too much money on the ones who are not like that at all. If you buy a 22 year old winger for 90 million euro and that player turns out good, that's great. But if you spend that on Antony, well then you know what you are getting, which is what they had and not just with one transfer but they did this with multiple transfers as well.
This is why I believe that they should be looking into players that they are buying into a lot more carefully. They may not find a buyer for 50-60 million range for Antony now, if they stop making these big losses and instead get some good players with the amount of money they have, they could actually build a team that will be consistently in top four and even fight for a title chance. They certainly have the money to do that, they just need to spend it wisely.