Kyrie trade was a calculated gamble. It didn't pan out but I wouldn't label it a disaster. It didn't set the franchise back that much in the grand scheme of things and, as Roy mentioned, Celtics were able to sell high on IT (who was never the same) and nothing outgoing really came back to bite the team in the butt.
I mean SGA would be nice. But who needs the reigning MVP and likely back-to-back winner.
I've said on here many times the biggest flaw in that trade that Danny made was not necessarily acquiring Kyrie but failing to pull the trigger on the necessary follow up trade. Kyrie was always a Robin, he needed a Batman, and I'm sorry Hayward wasn't a Batman. Had Danny pulled the trigger with the Spurs and acquired Kawhi, the Kyrie trade would have been like Ray Allen was while Kawhi would have been the KG. It would have cost Brown and Smart, but Boston almost certainly would have won the 2019 title that Kawhi led Toronto to if Boston had Kawhi, Kyrie, Tatum, Horford, Hayward, Rozier, Morris, Baynes, Theis. Team might have actually beaten a healthy Warriors that year and they would have steamrolled through the east.
You can't give up quality assets to acquire Robin and then not make the available move to acquire Batman.