He could be, but Celtics fans shouldn't lose sight of Big Baby's contributions to this team over the last four years as well as his importance to the 2nd unit.
For a player of his lack of height (for his position) and athleticism, it is truly amazing that he can score and defend as efficiently as he does. While you can argue that Baby fell in love with the outside jump shot a bit too much, he has a post game. He is a clever scorer with his fallaways, post up shots, and has soft hands which allows him to convert on lay ups even when there is coverage (easier said than done since most bigs are stiffs).
Don't forget that he was also a 6th man candidate last year. I'm not saying he ever had a legitimate shot at winning the thing, but he was a candidate.
Even though there are plenty of more athletic, quieter lunchpail type of bigs that would do the hard work at much less maintenance, we take for granted exactly how skilled Big Baby is. He is even a matchup problem for teams because of his diverse offensive game. Combine that with all the charges he takes and effort he's shown he will put in defensively, I'm not ready to say goodbye just yet. I'd like to see him back only because I have seen an improvement in his play over his career. There is an argument that I concede to that he needs to play within his limits more, and that is a coaching issue. Because I think once all the nonsense is corrected, he is an asset.