As far as him sitting on the mentor's chair, well, I don't think any of these mentors, minus Shankar, deserves to be called a mentor. With the profession of a teacher/mentor it is simply not enough to possess knowledge. In order to be a good mentor, you have to be able to convey that knowledge to your student. And that's where all these mentors lack. They don't tell them where they are doing wrong and the contestants continue to repeat their mistakes.
Also, you are forgetting that Pritam is a replacement for Bappi Lahiri. So his job is really to sit there and give useless comments and be completely clueless about the competition. At least he spares us by not singing songs in Bengali in every episode. 😆😆