I see your points and concerns.
System-wise Hayward is probably a great fit for the Celtics. Some here will worry about giving up a great perimeter defender like AB to make room though.
Kyrie's questions on defense are well known. If he can become even an average NBA defender that would be an unexpected but welcome improvement.
Perhaps the biggest question about him offensively as far as the system goes is, although Kyrie has great handles and offensive scoring capabilities, will he become a "ball-stopper" in Coach Steven's offense? That's probably the one thing we can't afford to have because his system is predicated on moving the ball constantly to find the best shot.
The second question offensively, how good is Kyrie's vision, really? Can his assist per game ratio rise as he is handed the "keys to drive the car"? Was it Lebron eating up all the assists because he was the #1 ballhandler, or does Kyrie lack the court awareness to become an elite distributor of the ball as a scoring point?
This is almost a brand new team with 4 starters changed from last season. Horford being the only returning starter. Who steps in to fill the shoes of the SG position? Will it be Jaylen Brown or Marcus Smart and can they play to the level of an Avery Bradley?
Talent-wise, I really don't see a more talented big 3 in the East outside of Cleveland. So unless we just flop out of the gates and never build chemistry, it's hard to see the Celtics finishing out of the top 2.
And last concern of my own, we STILL did not get better rebounding the ball despite all these big moves. Losing Zizic might have been the most underrated loss of the Trade. But imo this meant that DA valued Yabusele more. So what can the "dancing bear" offer us in season 1? Who secures the starting PF role, Marcus Morris, Jayson Tatum, or Yabusele?
Finally, the lottery jigsaw. Best case scenario, Lakers get pick #2, which conveys to us, and Brooklyn slides to the 6th to 8th pick in the draft. Worst case, Brooklyn wins the Lottery, and Lakers slip to 6th place or later. Who made the right gamble, Danny Ainge or Koby Altman?
My thoughts / predictions:
Hayward was a great signing.
Kyrie is a great scorer with some significant holes in his game. It's doubtful that he performs as well this season as IT did last year.
The concerns about IT's injury are overblown. He'll be healthy by playoff time.
The Celts won't finish with a top-2 seed.
We'll miss some of the grit and leadership we traded away.
The Lakers pick won't convey.
Despite Kyrie playing well in Boston, this will be a trade that hurts now and going forward.