I think this was a risky move that could still go end up being anything from a plus move, to a sidestep, to a backwards step.
I just don't know yet at this stage, and I don't think we truly will have any indication until AT LEAST the all-star break, because the success of this offseason is going to be very largely dependant on the development of Brown and Tatum and the rest of our young players, and we won't really see what we have with those guys until at least half a season is gone.
Kyrie, Hayward and Horford on a team full of nobodies is not IMHO enough to challenge Golden State (or perhaps even Cleveland). We need two very good starters (of the Bradley / Crowder calibre) at the other two starting spots to fill out the team well enough for it to be a true contender, and we'll also need a strong showing from our bench. That means we are going to need Brown and Tatum to step up in a huge way and prove they can be consistent impact players.
Smart (as the now longest tenured Celtic) is also going to have to prove he is ready to step up his game and his maturity to prove he can be a true leader for the second unit, on and off the court.
We also need Horford to be FAR more consistent in the regular season then he has been for the past 2-3 years. What we saw from him in the playoffs last season - that's the Horford we need out there every night.
And we need Morris to prove he can provide us with a steady and consistent starter's production (rather than the streaky play he's shown so far in his previous stints).
If all of that comes together perfectly, this grade may well increase to an A. If it fails to come together, then the team may regress, and this grade may fall to a C.
For now I'm giving it a B to factor in that we got two legitimate All-Stars, but sacrificed a LOT in order to get them.