OK, so the OP clarified and I think his point is that he is comparing the relative value of the replacement for Horford, Kyrie, and Morris (and others I guess). It is hard to line these up exactly but this is what I see:
Walker replaces Kyrie
Kanter replaces Horford
Poirier replaces Baynes
LangfordWanamaker replaces Rozier
G. Williams (?) replaces Morris
Now I know that some of these are not going to be direct replacements. For example Robert Williams may be more of the direct replacement for Baynes and Poirier then replaces Williams in a way. No matter how you look at this, all of these are steps down or back. Going from Morris to G. Williams may be the biggest step back.
To make up for all these steps back, we need to see improvement in individual play of Hayward, Brown, Tatum, Smart, and R. Williams. Many of these players could very well be very much improved. Other than Hayward, these are mostly young players who should improve. In the case of Hayward, it is year 2 after a gruesome injury.
Don't get me wrong, I am not feeling good about all this. It seems we are behind where we were. Last season we had a more talented team that underachieved. The season before that (after Kyrie injury) we had a less talented team that overachieved. Hard to say what we are going to get out of this group.