What a weird thread. We had £150m worth of attackers, Mata, Lukaku and Martial on the bench who didn't play either. Your example doesn't highlight a poor transfer strategy, but more shows we're now seeing the effects of Ferguson's lack of planning and reliance on all his star players being over 26-27. (Evra, Rio, Vidic, Valencia, Carrick, Scholes, Giggs, Rooney, RVP... probably some others I missed out).
Shaw was worth the money paid, at the time.
Rojo was/is worth the money paid, at the time.
Blind was/is worth the money paid, at the time.
Darmian was worth the money paid, at the time.
Bailly & Lindelof, who knows.
I kind of see your point but I think in football you need continuity. Something I've realised is that the players Man City have managed to keep are Kompany, Toure, Fernandinho, Silva, Aguero... same with Real Madrid; Marcelo, Ramos, Kroos, Modric, Ronaldo, Benzema - ours are DDG, Smalling, Jones, Young, Valencia, Carrick and Rooney until last year.