It is a good investment for Manchester United, Diego León is a young talent and I think Manchester United needs to starting replacing the old squad with new young players. This signifies Manchester United aim in trying to build for the future. Chelsea made a lot of young signings last season and people laughed at them but look what the team now, they are playing well and winning games.
I do believe that Manchester United should include one or two new players and give them a chance to see how they fit in the team. The performance of them is on the decline and we are seeing this in this season where they have won only 5 matches in premier league and lost 6 matches. They aren't in the top 10 team currently on the points standing and it is obviously against their standard. Also keep in mind, just bringing new blood in the team won't have an immediate effect but in the long run, it will be beneficial for the team.