Re: How powerful is a Galaxy class starship?
The Enterprise-D was well short of the historical age of second line status. Which was probably something like twenty plus years if we go by Star Trek III or lines from Conspiracy and Yesterday's Enterprise. Also previous ships were not obsoleted solely by technology but to a large degree by ship displacement. The Galaxy is still the largest combatant by size.
In relative power it probably still better than a vast majority of Star Fleet save the brand new Sovereign class. I don't believe the Akiras to be all that recent(Nebula and Akira registry number comparison) and would have been plagued by the same peacetime design considerations all pre-Borg ships were built to.
"Your knowledge of Klingon curses is impressive. But, as the Romulans might say, only a Veruul would use such language in public"