Good post.
I think people can be so extreme in their views. Of course we haven't signed 40-50 players for the amount that we have with NONE of them being United quality. That would be insane.
Yes, we have been poor in the transfer market. There's no way around that. But at the same time, there is good reason to believe that some of the players (also some that I didn't mention) would have been highly successful under Fergie, Ancelotti, Klopp and Pep. The circumstances matter.
Yea.
now to answer the OP question, for me I’ll go for:
1. Bruno - country mile and all that. One of the best deals in the PL in recent years. Goals, assists, attitude off the pitch, on the pitch. United have had several players with issues during these years, but four consequtive managers have looked at that dressing room and found Bruno Fernandez not only not a problem, but one of the best bets for a solution. And cheaper than Pogba, Lukaku, Maguire, Di Maria …
2. Alejandro Garnacho - the most likely way Garnacho is not going to turn us a huge profit, is that he stays at United well into his decline. And that is not enormously likely.
3. Juan Mata - what decides many a player’s legacy is memory, and at United that means we always remember two things: The start - when players come with huge expectations (cos we bought them) and is bound to disappoint. And the end - when players have declined, does not fit the team any more or have turned into a mental wreck from the United pressure. Juan Mata had a long spell with over 200 games were he was one of our most important and most watchable players, and he wasn’t even an ass!
4. Daley Blind - came on the cheap side, was a joy to watch, surprised positively and a good influence on the dressing room by all accounts. A shame he played for the wrong Dutchman from our perspective.
Honorable mentions to Luke Shaw (One of our best players for not enough time, and we must add to his price what it cost to have Rojo, Telles and Malacia breathe down his neck); Rojo/Telles/Malacia (for making Shaw good); Zlatan (what a gas until he went out of gas); Lindelöf (when I imagine the amount of games Phil Jones would have played injured without the Swede around, or Tuanzebe would have played nervous, Bailly insane, Mengi clueless, Maguire with broken confidence, Varane with ‘issues’ etc etc…); Cavani, Romero, Heaton (free and handy to have around).
a special nod to Pogba for getting Mourinho fired. He played a few very good games, but a player bought twice for record fees, leaving for free twice, that’s just totally awesome in this light, unbeatable really.