Celtics won't be able to just stand pat forever. The team they have now is not good enough. And eventually you're going to have part with some of these players to go to the next level.
Even if you plan on relying 100% on the draft, you're still going have to consolidate assets somehow, or else you end up essentially wasting picks like the last two drafts.
I like Rozier and all, but in this league PGs are a dime a dozen. And even though it's still early in his career, I will be shocked if he ever becomes as good as someone like Ibaka is. Me personally for Rozier and a late 1st I would've pulled the trigger on that with no hesitation. Obviously it's not the end of the world but w/e