I had a response to Big typed and for some reason it didn't go through and I lost. Basically, I would have signed a combination of lesser players than Horford last summer, with less long term money locked up. There were any combination of players that could have been signed, including just keeping Sullinger (of course they could have kept him anyway). Speights, Ezeli, Biyombo, even Howard, all would have been interesting. I mean is the team really much worse if instead of Horford and Zeller, it has Howard, Sullinger, and Speights (you could even still have Green if you just cut Young as well as Hunter). The other option would have been just sign some 1 year deal type players (like Sullinger and Speights) and then go into the deadline and acquire someone like Ibaka or Noel, or frankly both of them since you could still have max cap room and keep one of those guys this summer. Again is the team that much different if instead of Horford and Zeller you have Sullinger, Speights, and Ibaka or Noel. I don't think the product on the floor is that much different, but in the latter scenarios you don't have nearly 30 million in salary locked up in a player that doesn't fit the age timeline of the rest of the team and isn't a #1 player. heck at this point Horford probably isn't even a #2 player, and by the end of his contract might not even be a #3 player. Horford was a bad signing at the time. A few good playoff games doesn't change that.
Biyombo signed a monster long term deal with Orlando, he never would've come to Boston for a 1 year contract. Howard, similarly, would never have taken a shorter deal with Boston when he had his hometown offering him good money for 3 years. So those two are out.
Ezeli didn't play a game this season so that would've been wasted money. Speights is interesting but a career backup who would've been fighting for minutes alongside the rest of the big men who weren't good enough to start.
Acquiring someone like Ibaka or Noel means having to deal with their impending free agencies this summer as well which means you're either planning making them one of your big expenditures (neither are as good as Horford) or letting them walk which means giving up assets for a one year rental in a year in which the team wouldn't be competing for anything, especially because the team, in this hypothetical, would be worse than they were in actuality.
To asnwer your question of whether the team is much different with your list of players, the answer is an obvious yes. Our current team is much better than the one you're talking about. For one thing, you can't play 7 players at the same time so you're not replacing Horford is 3 guys, you're replacing him with 1 guy and the other 2 are sitting on the bench.
And if the whole reason for not picking up a superior player (Horford) is to retain max level room for 2 players this summer, who are those players that are more worth it than Horford and are going to come to Boston? And if it's not about this summer, then none of it makes sense to me, because after this summer, IT and Bradley will be looking to get paid which means the space won't be there, anyway.