Last season may have had better 1-on-1 talent, but this is a better team. Kemba is way more team-oriented than Kyrie is, even if he is (slightly) less talented. 2020 Tatum and Brown are much better than their 2019 versions. 2020 Hayward is head and shoulders above his 2019 self, and quite frankly more impactful than Horford was last season.
Theis has played quite well despite his limitations, and hopefully Kanter can contribute with his offensive repertoire.
Rozier was pretty awful in 2019. I'll take Wanamaker over him for spot minutes (but 2020 Smart is a big upgrade over TR3).
There were too many egos on last season's squad. I'd rather see Kemba/Smart/Brown/Hayward/Tatum get 36-40 minutes each than have to find a way to get Irving/Rozier/Brown/Smart/Hayward/Tatum/Morris all adequate minutes so they didn't pout.
2019 was one of the least enjoyable Celtics seasons I can recall. We definitely have seen worse teams over the years, but they didn't even look like they were having fun. They may have worn the same uniform, but they weren't a team. I put a lot of blame on Brad (and Horford), but seeing the camaraderie this season makes it pretty clear the problem was Irving, Rozier, and Morris.