Horford should had stayed, he thought Celtics gotta be bad this year but they surprise everyone except first round exit
In retrospect, sure, it ended up that BOS had a better season than GSW. At the time though, I thought going to GSW made way more sense for Horford. And in the end, he only was able to play 45 games. In those games, his production was very comparable to what he did the last season in BOS, especially when you consider his minutes were down from about 27.7 min to 21.5 min. I did not see any of his games this season but I am not sure he played all that bad, when he played.
All that said, I don't see him as what BOS should be looking for. I expect that teams like LAL, NYK, even SAS would show some interest. His available games and minutes will probably continue on the downward trajectory. BOS needs a starter or a regular rotation big, not limited games/minutes big. It is possible BOS could add both, but I don't see it. I would expect that if Horford gets a good offer in a good situation, he will play another year, if not, he will simply retire.