That's kinda my point (re: Butler/Simmons) - they simply couldn't work all that well together, because they're both so dependent on the ball being in their hands. If you look at the playoff series, it was rarely BOTH of them scoring/facilitating. It was usually one taking over, and the other disappearing. If you look at the Brooklyn series, that swung back and forth pretty hard.
Regarding the fit? They're going to miss Reddick on offense, but I really believe they're going to work better in the half-court because of Horford. He gets to play the stretch-4, and lets Harris do what he did best in LA; play SF with the ability to spot-up shoot threes. And that doesn't even account for Richardson, who I'm sure you'll attest isn't quite Jimmy Butler, but I'll argue he works better OFF the ball, is at least as good an outside shooter, and is about ten thousand times better on D than JJ Reddick.
Again, teams simply aren't going to be able to collapse as much as they did last year because literally everyone else who is on the floor with Simmons at pretty much any point now is going to be able to shoot. And if they start moving out to contest shots, Simmons is just too fast for big guys, and too big for fast guys.
And if Simmons does develop a 15-foot jumper? Forget about it.
Anyway, we'll see. If they don't make the ECF this year at the very least, someone should be fired.