For me i will always regret not having seen the Sovereigns,Intrepid,Prometheus classes in the Dominion War,it was very weird having them in the Movies other series...it was a huge problematic for them to say and i quote :
''The Enterprise-E is the most advanced starship in the fleet.'' (
''Prometheus class designed for deep space tactical missions''.
(VOY ''message in a bottle'')
''Intrepid class,designed for combat performance''.
yet Starfleet does not use them
i think the only thing logical to comfort my mind i could think about is that all 3 classes were used but not on screen.