One of the assumptions was that proliferation of small "starship" qualified warp capable craft (as opposed to smallcraft) was that ships were finally large enough to actually carry a fair number of them, the growing size of Starbase facilities, and the fact that shipboard industrial replicators might allow starships to modify/customize them to their own satisfaction.
We know that Sisko referred to runabouts as "starships" at several points. So maybe they can in fact go at at least warp 5 (old scale) and have dilithium reactors. I'm partly basing that by the by, on the fact that NX-01 being a warp 5 ship and being a "starship" seemed to be a big deal.
Perhaps dilithium reactors went out of style for a while after NX-01 and were only revived around the time of TOS.