Here's the problem with this trade. I think most people like the idea of Aaron Gordon more than the actually on-court impact.
He's a power forward in the modern NBA, but he tries to play like a play-making wing. He can't shoot from the outside (31% for his career), but he still launches 4 a game. He's isn't a good enough ball-handler to break down his man off the dribble, but he tries to do that all the time. Like 38% of his shots are from mid-range. The idea of him as a defender has always tantalized, but he's not locked-in enough and his defensive instincts aren't great (.5 blocks and .7 steals per game even though he is one of the most gifted athletes in the NBA).
I've always liked the idea of Gordon, but I'm not even sure what he gives to the Celtics that Hayward doesn't bring. Hayward is a better defensive and offensive player in just about every way. I'm not even completely sure Aaron Gordon would start on the Cs over Smart.
When you break it down, this trade is about your evaluation of Mo Bamba's talent (Aminu is injured and may be out for the year), which is a highly debated topic.
Even if Bamba becomes a solid NBA starter in 2-3 years, I'm not sure that trade makes sense.