I think this is basically right. They've been unable or incapable of really implementing a coherent plan for the last few seasons due to the Wenger situation and the clashing time horizons it involved (him clearly having incentives to win now, despite that looking more and more unlikely over time).
Its not an insurmountable problem going forward, but definitely one that needs to be handled well (which it might not be). As you note, in football it just doesn't pay to go into a complete rebuild. So the answer is really to build a team that relies upon a few veterans to remain competitive - Ozil, Auba, Mkhitaryan, Lacazette, Koscielny, Monreal - while making a concerted effort to buy and integrate a new core of younger players and improve upon some areas (CM, CB, and some more dynamic wing players) that have become weaknesses. The best thing they have in their favor in this regard is that all the veteran players just mentioned either signed new deals recently - knowing that Wenger would likely not be around for most of their contracts and probably also realizing that this team wasn't going to win the Champions League or anything in the next couple seasons - or, in the case of the defenders, are longtime club servants probably OK with sticking around. But you need to bring in the right new manager who will get along with those players and keep them on board. And you need to do a good job with recruitment and player development if you actually want to get better. Easier said than done for sure.
Its unclear if he would really leave Juve but I've heard some talk recently about Allegri wanting a new challenge (and a much richer contract) and I think he would be an excellent choice if truly available.
