Well in the Champions League he has scored a couple of goals so far. In Ligue 1 it's definitely not going well for him. If I were Pochettino I would also leave Ramons on the bench. He doesn't seem to be at top level anymore. Way too bus with things that happen outside the pitch. Crazy that PSG decided to pay him such a high salary although they knew that Ramos is frequently injured and misses most of the games these days.
From my point of view PSG signed Ramos so as to add his wealth of experience into club defence, UCL trophy is the main target for PSG in order to win that coveted trophy they need to improve on their defence line and with the signing of Ramos that area of the team would have been taken care of, it is not compulsory Pochetino plays Ramos in every league-1 matches, which I agreed with you, of course PSG has dominance in that league but their main objective and aim is winning UCL this season thus has to fix their team in every department once they achieve that they might sell him.
this is indeed quite good, but on the other hand by making him linger on the bench it will actually affect his performance because even though he is a great defender but when he is not played for a long time it can actually interfere with his performance because he has to adapt to the field .
If you look at it from this angle, Poche should be able to act more wisely