Boston adds a bigger wing that can get you 18-20 points on any given night. Fournier also adds experience and a veteran presence in the locker room.
I don’t see why the Magic don’t do this. Fournier is on an expiring deal, and he is not really part of their future plans. Adding a young combo guard with upside and a late 1st round pick is not bad at all for a rebuilding/reloading team.