That specific quote is but he repeated it later in the season as well but the quote you mention is the most recent.
I interpret his most recent criticism as again being primarily down to attitude, work rate etc but ultimately who knows. I agree if he's not improving then there is no point, just like I think its pointless keeping him if he doesn't want to be here.
Maybe it is unprofessional but I was equally unprofessional at that age. In-fact even at the age of 38 id say my ability to perform to my best in a job is influenced by how happy I am in said job... even if its only at a sub conscious level. His attitude was never criticised at any of his other clubs with both Charlton and England u20's manager speaking highly of him, his attitude must have also been on point in Leipzig hence why Hassenhutl is supposedly interested in signing him for Southampton