There is another piece to this that we don't know so it is hard to grade. The Celtics save around $10M in 2021-22 and I think $12M 2022-23 (more if they release Horford). The piece that we don't know is whether this savings allows them to do something they otherwise would not have. If that ends up being nothing, than I give this a C.
In looking at the team for next season, there is a lot to like. I break it down as follows.
Wings:
Tatum, Brown, Fournier (assumed), Nesmith
Very strong, maybe even the best group of wings in the league.
PG/Combo Guards:
Smart, Pritchard, Langford, Nadar (maybe)
Walker is gone from this group so some vet scoring is lost but this group is still decent. Certainly serviceable. I have Langford here as I don't really see him with enough size to be a true wing.
Bigs/Swings:
Horford, Thompson, RWilliams, Parker, GWilliams, Moses Brown, Kornet(?)
Still a very weak group. I guess Horford and maybe Parker will improve us. Not sure any of these players are really starter level. All kind of fringe starter at best. Parker started like 25 games for Atl in 2019-20 putting up 16 and 7 or something like that but I don't see him starting.