Either Can is so super shit a 33 year old Khedira is a better option or Sarri is an idiot. I go with the latter.
Khedira is better CM. Can is a DM who is clumsy with the ball, erratic and slow in possession.
On footballing level imo its completely right to exclude him because our squad is too big and he is most expendable in current circumstances, with Bentancur. Every other player is a positional must to include (keepers, defenders and attackers) or are ahead of him in pecking order (rest of the midfielders except Bentancur? Not sure why him too now).
The only thing that's wrong is promise him CL squad spot so he stays, and not give it. I doubt it was Sarri, so likely Paratici promised something he couldn't guarantee.