The only real problem was when Riker didn't order to fire everything at the Bird of prey.
He probably did. After all, the ship did fire single phaser beams, which is the very definition of "everything" from the TV show (that single occasion in "BoBW" with the impossible pylon beams notwithstanding).
The plot isn't unpalatable in that sense at all. Dialogue as such covers all the plot holes. Shields are useless because the man operating them has been co-opted. Klingon shields in turn are holding in a twist that surprises even the Klingons themselves - but the audience
shouldn't be surprised, as the tech wizard Soran had previously promised to do something about the fact that the villains were ridiculously outgunned. And yet the E-D fights back, constantly firing weapons, as we can hear from the background noises.
It's the visual presentation that is lamentably lacking: we see just a small fraction of the battle, omitting all those moments the heroes are firing back. And we never get the scene that's probably playing out several times as the battle proceeds: Riker orders shields adjusted some more, LaForge duly adjusts them, and the Durases watch and learn and do their own adjusting.
A "plausibly" superior enemy would have been no fun. The movie is about a bitter old man trying to change the unfair universe to his liking, and another opting not to; it's only fitting that the climax features a space battle between our heroes and a tiny, rusty has-been of a starship, and a wheezing and coughing fistfight between said two old men - both of which the hero side actually loses hands down.