Think you answered it yourself. Full rebuid mode, Sid Crusty is 32 turning 33.
Scored 100 pts last year sure. But you should note that it took 5 years in between before he did it again compared to doing it 4 times in his first 5 years.
Try and get max value since he's a big name but yeah if you're in legit full rebuild then trading Sid Crusty is the move. If you're retooling then that's a different story.