Actually there are some good Man United players and their talents are very good. It's just that, as you said, many of them either dropped in performance or because the previous coaches were not able to optimize them, so it was really like a wasteful player purchases. It's just that, some ex-Man United players when after leaving and entering another team, they became good again at playing.  

And I read the news of Man United recruitment here, but for the left back:

Source: The agreement between Man United and Cerro Porteno for Diego León
There has been some controversy surrounding the signing, but the bottom line is that an agreement is in place for Diego León, a 17-year-old left-back who currently plays for Cerro Porteno.