The winner/loser of the trade wont be decided until a year or more down the road. there are some uncertainties in it.
1. How good with BKN 18 pick be? If it is top 3, celts gave up a lot. if BKN improves enough(with enough other teams tanking) that it ends up 5-6 then advantage boston.
2. How healthy is Isaiah, and do you view him as the piece who was going to bring you to a championship? Ainge made an interesting comment with "irving fits our timeline better" which means Ainge doesn't really view the c's as "true contenders" until 2-3 years from now. When Irving hits his prime and jaylen/tatum are developed.
3. Will Thomas/Lebron stay in Cleveland? if they both bolt next year, all the Cavs are banking on is how good the BKN pick is. Or, the pick could be #1, Thomas stays and they trade the pick for another star. It really could go either way.