If Horford opts in, Kyrie walks, we resign Rozier, and maybe another minor move or 2 (Morris, backup pg), then I'm OK with that. I think we are still a top 5 seed in the East. Contenders? Not strong ones right now on paper, but Jaylen, Jayson, and Terry are all at that age where one or more of them could make huge leaps in their game which could make us a better team that we'd be expecting. Gordon could make a comeback. There's a pretty high floor with that roster, some reasonable upside, and overall I'd be happy with it even if it's not considered "contenders" in the preseason.
I really don't think that is a top 5 team in the East next year.
Milwaukee - clearly better (even if they lose one of their free agents)
Philadelphia - clearly better (even without Butler and Harris, I still think they are better, but I think they keep at least one anyway)
Toronto - clearly better (even losing Kawhi I think they are better, though it would be close)
Indiana - clearly better (assuming Dipo is back)
Brooklyn - if that is Irving's destination then they are clearly better (if he ends up in NY that is a different matter)
New York - free agency/trade dependent, but a very good shot at being clearly better
I also think there is a very good chance that Miami, Detroit, Orlando, or Charlotte end up better
I think that Boston team will probably make the playoffs, but it will be somewhere in the 40-45 win range and frankly I don't see many paths to being much better than that unless Tatum turns into Durant.
Lol classic mind-boggling Moranis logic:
Milwaukee - definitely better, though it would be close if they lose Middleton (which is unlikely)
Toronto - with Kawhi? Definitely better. Without Kawhi? Uh, no. Who would they have? An aging Lowry, Green, Ibaka, and Gasol with Siakam as their number one option? As much as he improved this year, that offense would be less than mediocre without Kawhi. Assuming a lineup of Rozier, Brown, Tatum, Hayward, and Horford with Smart, Baynes, Mook, etc. off the bench that's definitely a better and more well-rounded team than Toronto sans Kawhi.
Philadelphia - same boat. With Butler and Harris? Sure, they're better. Losing both of them? Again, no. This would be the same Celtics team that beat Philly in the 2018 Eastern Semifinals + Hayward and + significantly more experience and expanded roles for Tatum, Brown, Smart, and Rozier, all while facing a significantly weaker Philly team who gave away significant assets for Harris and Butler and have nothing to show for them.
Indiana - hardly "clearly better". With Dipo they're about equal with that iterations of the Celtics.
Brooklyn - dependent upon free agency, but I don't see anything that would make them better than us next year. If you add Kyrie and Durant, then that's clearly not better given that Durant wouldn't play next year. If you add Kyrie to Russell, I think that team is similar in overall talent and ability to Boston and Indiana. While that pairing would be dynamic offensively, that's probably the weakest perimeter defense any team has started in a long, long time, which will cause significant problems with their overall defense in today's NBA. If it's something like Kyrie and Butler/Harris, I still don't see that as putting them better than this Boston group.
New York - again, hard to say due to free agency, but I don't think they're getting the big free agents that they think they're getting this year.
Orlando - Depends upon their free agency, but I think they'll end up a bit better and will probably be in that grouping with Boston and Indiana.
Miami, Detroit, Charlotte - give me a break.
Per usual, you significantly underrate our players and overrate other teams' players. With expanded roles, all three of Tatum, Brown, and Hayward should put up better numbers next year, along with Hayward getting healthier and more confident overall. I'd expect next year's team to be a better version of that 2018 playoffs team with one of Brown or Tatum - maybe even both - making significant leaps with expanded roles and at least one of them reaching their first All-Star game.