So your logic is based on two players who didn't go out on loan? I understand players can improve at different clubs. Our Mo Salah is not Chelsea's Mo Salah.
We have done it and I don't think it's beneath us but I honestly can't see who would be out there available to loan who would improve us. If we're loaning from top teams they'll want guaranteed playing time which we can't offer either
There are players at top clubs that cannot get guaranteed game time but they believe that at another club they would based on their quality, not on agreements. When we buy any player there are no guarantees of game time or if they will even play
Sometime its the system, look at Antoine Griezmann Barca struggling to adapt,
That fact that they do not play regular at that club does not mean that they are poor players, hence why I use Van Der Vaart and Robben as examples.
It could be the system or role that the manager wants them to play.
A couple more examples to go with Mo at Chelsea... Sane for City( for me a way better player than Sterling) for some reason pep does not fancy him, KDB for Chelsea,not rated by Jose, Ousmane Dembélé for Barca, and of course Philippe Coutinho, great for us, not so great for Bayern and Barca. Barca would loan him back in a heart beat, and if not for the stick that he would get from the Fans I believe that he would glady come, but he knows that he has burnt that bridge
As I said there are so great players out there , some simple do not fit their current clubs systems or the manager game plan and have not broken into the team are getting little to no football,and would jump at the chance to revive their career and at least on loan we get to test drive the player in our system first