Dort can guard the 6’7 wings. You havent watched him enough if u think otherwuse. N his handle is much better than Buddy’s.
I mean, he can but it's not ideal. It's the same issue the Rockets faced with PJ Tucker at center. Sure, he can man up a guy in the post for three or four possessions but the bigger guys are just going to play over his head like Ingram did in their matchups this season. Dort looks like he'll be a solid on the ball defensive role player guy in his career, which is nice to have but not if he's your go-to small forward. This is actually a similar problem we're seeing with CoJo in our three guard lineups as he usually gets stuck on wing and outsized regardless of good defensive effort or positioning. If we're going to trade Buddy for a dude to guard wings, I'd rather he be an actual wing and not a short guard we're forcing to defend out of position.
On the issue of Dort's offense, Dort currently has a 1 to 1 assist to turnover ratio and he struggles to create for others or himself whenever teams actually bother guarding him on that end of the court. As a spot up shooter, he'll probably end up settling back down around the .350 range, which is what Buddy is shooting now despite being in the midst of a horrific shooting slump.
I realize Buddy is like enemy number one for you and Dort is apparently your new player crush so this is like a wet dream for you but selling super low on Buddy and taking on three seasons of Horford's max contract for a fourth guard is how bad teams stay bad.