No, FC happened after BOBW.
In BOBW the Admiral states Starfllet was already in development of better weapons, shields & ships but they just hadn't finished building them yet. BTT FC happens many of those weapons are already installed on Starships. Proof is Voyager now equipped with Tri-Cobalt torpedos. The Borg in FC weren't weaker, we had upgraded our shields & weapons.
It had been four years inbetween BOBW and FC. Plenty of time to upgrade a fleet.
No. It had been 6 years and in that time the Borg are also upgrading their technology at a MUCH faster rate. So nothing Starfleet comes up with could ever stand a chance.