Cancelo really can't defend, it's very clear he can't. He makes up for it because of his excellent attacking attributes, which allows him to join up in midfield.
Pep doesn't even play him in defence.
And Rodri is more than good enough when he has legs around him to enable him to do what he does best, which is what Bernardo and Foden energy have afforded him in the system personnel upgrade this season.
My point being, they are all good players made even better by a system.
In Dias' case, he is a much better player when Stones is next to him.
Laporte has not been great as you concede, I just used a less polite term in crap.