Very true though , when he was good he was very good and now we are weakened in a key position , no bones about it
So, to keep him, we have to make sure he's happy by playing him, even though he's playing 'well' in about one in ten games, and providing the odd half-decent cross.
Presumably, that would be at the expense of a better performing, more reliable player (i.e.Ake or Laporte), leaving them on the bench wondering what they have to do to get a start, and concluding that arguing and throwing a hissy fit like Cancelo was the best way.
Cancelo has been a weak link for ages. He can't defend, and he's too erratic going forward to link up with the left-sided forward (Foden, Grealish).
He was the same at right back. He'd drift into midfield, but to lesser effect than Walker or Lewis.
Walker can overlap, shift to WB or CB if needed, and will do a top job.
Lewis can overlap, be used as a WB or midfielder if needed, and has shown he can do a top job.
Cancelo lacks that versatility, and truth be told, he's been lucky to get any starts this season imo.
He's a bad apple. Good riddance to him.