While Enterprise is conveniently the only ship around in TMP, the novelization talks about massive stationary firepower around Earth. This naturally turns out to be no use at all against such a technologically superior enemy. Don't recall if any of that dialogue made it into the film.
CHEKOV: All planetary defense systems have just gone inoperative!
Fleshlights?... and Light has been around for some time also...
Flashlights, Phasers, Lasers, Disruptors.