I think they would have been a top 4 without Tatum if they brought last year's group back.
I am not so sure about this. I think you are factoring in that White, Pritchard, and Hauser are all playing to the same level they did last season. Holiday is better than Simons, but his numbers in POR are not better than Simons' numbers in POR. If Holiday were still in BOS, would the same thing be happening to him that is happening to White? I think there is a good chance. Porzingis for sure improves our big rotation, but he hasn't made ATL a top 4 team. Horford is hurt and Kornet is a bench player.
I wonder where the team would be if just White, Prichard, and Hauser were playing the same as last season. How much better is this team just from that? One factor no doubt is that Tatum helped make these players better. He probably would help make Simons better too.
If not for the Apron penalties, BOS would have run the team back. If they had kept everyone, the team would be better. Maybe White would be playing better too. Not sure where this gets the team though.