You're also forgetting a hopefully big 2d year step up from guys like Darby (to truly elite level), Miller, K. Williams and O'Leary.That plus familiarity with the schemes and, as you note, TT having more experience, are the reasons for potential optimism.
That said, they need to pick up several (2-3) starters in this draft to fill big needs at RT, DE and LB. Personally, I'd
like to see them take a DE or edge rushing LB in the 1st, RT in the second, LB in the third and BPA thereafter to fill depth at WR, S, CB and DL. Those comp picks may help there.
It would be great if we could fill at least one hole in FA, but absent the long-term signing of G or G, I don't see it.