I agree with your concerns, but you won't get a lot of sympathy from certain folks around here.
Many here interpret statements like "Maybe Kyrie isn't the kind of guy you want to build around" and "Maybe it's not a good idea to trade our best assets for a guy who has made clear he wouldn't be inclined to stay" as "We should accept mediocrity and not contend for the next 10 years."
There are a couple of possibilities that are scary to me.
The Celts could trade for AD and get a short term commitment from Kyrie and then lose both for nothing.
Or, the Celtics could sign Kyrie long term, trade all their pieces for AD, sign AD long term, and then both guys end up being injury prone and super mercurial / unhappy and the team underachieves as a result.
Not sure which is scarier. On the one hand, the team is left basically having to start over a year or so from now. That's a disaster. On the other hand, we all spend 3-5 years following a Celtics team that is basically more of the same as this past season, albeit with more talent.
Maybe talent is all that matters and the team should take the chance regardless, because the alternative is irrelevance. I suppose you can't pick and choose which superstars become available when you have the assets to make a move. If the team moves on from Kyrie and doesn't trade for AD, there's no guarantee that they're in a position to make a move for a franchise talent the next time one becomes available.
It's a tough spot the team is in this summer. Though I think it's healthy to remind ourselves that many franchises in the league would be thrilled to switch places with the Celtics.