I think most people were saying the same thing last year in relation to Alonso-Azpi/Zouma. Was he an upgrade on either?
Now, towards the end of the season people not many would put Zouma in the squad at the cost of Alonso not being there.
I'm fine if Conte thinks Rudiger is an upgrade on Cahill. We also have to have squad depth in order to play more games. We can't just upgrade our first 11 every transfer window.