And you haven't invested poorly at the beginning? For every Aguero, Kompany, Silva, De Bruyne.. There are the likes of Robinho, Santa Cruz, Negredo, Bony- member him? Jovetic, Javi Garcia, Mangala, Mendy, Ake...
I mean just look at the team Fergie left
https://en.wikipedia.org/wiki/2012–13_Manchester_United_F.C._season#Squad_statistics
The back 4 needed a complete overhaul. Yet it didn't happen. Same for midfield
It took you over 550m€ to spend to actually get to an UCL place(2007-2011) or over 700m€ to win the EPL title. How many of those record signings were actually there when you won your first title in 2012?
You have the ability to replace an expensive signing that was a dud in the next 2 or 3 transfer windows while at Utd those same shitty players keep getting chance after chance.