If Kyrie leaves, it'd feel bad but I wouldn't say it's a moment that "dooms" the franchise. We'd still be in solid shape. No, maybe not championship contender, but still no doubt a playoff team that can still get better and make an addition or two going forward (via trade and/or draft - MEM Pick) to launch this team. Also, hope the Jays keep growing and Hayward regains some all-star form next year.
I'd love to keep Kyrie, but in a way it'd also be a real bad look for him if he made that announcement in October in front of the TD Garden crowd that he was willing to stay "as long as you [C's fans/management] feel the same way", then the C's made a max offer but he still chose NYK. Now if the C's thought his injury risks were real and didn't offer him the 5/188M max, then that's different, but otherwise I still feel he'll choose 188M to stay here as opposed to going NYK (w/Dolan still there) or LAL (w/Lebron) for 139M (50M less).
In a way, I actually think we'll all be at so much ease after this summer, because regardless what happens at least we'll likely have better clarity about this team going forward. Kyrie's FA, the AD trade dilemma, etc. should all come to a "conclusion" this July and from there, we'll know what to expect and have a better idea on things.
With that said, I do think it's ridiculous for anyone to suggest we're a better team w/o Kyrie. If you actually think we're capable of beating the 2019 Raptors, Sixers or Bucks in a playoff series this year without him (Kyrie), then boy you'll be in for a surprise.
Last year was a great run but in fairness, it helped we had home court (we were 1-7 on the road last year's playoffs) and we lost in the game where we truly needed a player of Kyrie's caliber. Plus the Bucks actually improved AND got a better coach than what they had last year (which makes a big difference).