Yeah. Shame on Starfleet for not being more serious about fielding a warship.
Er?
Aside from the possibility that Starfleet SIF (or warp field) technology may not be sufficiently advanced enough to allow the construction of starships as large as the Scimitar, there's the whole issue that until recently Starfleet seemed to be very badly overstretched. When you need to patrol a sector, which is better: a single, massive battleship able to tangle with nearly any other single ship around, or four smaller yet still capable cruisers? The cruisers, in this regard, are the superior choice because they can be in more places in once than the battleship can. If something too big for one cruiser to take on wanders into the sector, the cruisers can regroup and gang up on the bigger ship.
Roddenberry envisioned there only being
six Galaxy class starships to begin with. The non-canon TM suggests that the Ent-D took around
thirteen years to build. And even though we only saw
some of the Galaxys during the run of DS9, they would
still only comprise a
small fraction of the entire Starfleet. I can't imagine more than a very small handful of superkilometer ships being built by the Federation... and when they're still rebuilding their fleets from the Borg and Dominion attacks, the important thing at this time would be towards the smaller ships that can patrol and secure Federation territory.
They came all the way from Romulus. Considering that nearly every other ship we've seen from them in the TNG era was a D'Deridex, I'd say that sending anything else is a big stretch for them. Even having anything else. I'll concede that they may not outmatch the D'Deridex overall (but that's only a possibility, not a given), but they must have some advantage in order to even exist.
Remember TNG "Tin Man"? The D'Deridex warbirds can't keep pace with a Galaxy class, let alone the faster
Soveriegn and
Scimitar classes.
I'm not saying pound for pound (although I'd suspect that all three ships together outmassed the Scimitar - but that's a guesstimate). I'm saying ship for ship. Regardless of the reasons, the Scimitar is superior to any other individual ship the Feds and arguably the Romulans have. Maybe a Fed ship with the mass of the Scimitar (and proportional abilities) could beat it. But Starfleet didn't build anything like that. They didn't send the E-E up against its mass in Scimitar. They sent it up against the whole thing.
Starfleet had no idea that the Remans had put together the
Fan-wank... er, excuse me, I meant the
Scimitar, nor that the Ent-E would engage it in combat.