- Around the 2380's, Starfleet focused their resources on building a huge evacuation fleet to help the Romulans.
- The entire fleet was then destroyed.
- According to Clancy, Starfleet did not have enough active-duty ships left to replace them, besides the fact that after the attack, the Federation decided not to continue the effort.
- Immediately after the attack, Picard is even having trouble assembling a new fleet made up of mothballed ships with reserve crews.
(And I'm not even going to get into the whole Dominion war aftermath or Borg incursions and how that could have affected Starfleet.)
So the implication of all this is that Starfleet seems to be quite weak post-2386. And yet, by 2399 we see hundreds of ships, all the same design, seemingly new designs, seemingly super-fast and super-powerful, all in one fleet that was apparently very easy to assemble with very short notice. Hmmm.