Symptoms:
Bad acting. I guess Frakes & Sirtis are several years outta practice (and shape). And who wrote that dialog anyway?
Bad effects. Can't think of a good excuse here. I mean, really: stars between the camera and the ship?!? (space-fireflies???)
Bad production. Tons of obvious overdubs. They must've already pink-slipped the sound engineer. (Not to mention the amateur-looking phasers...)
Why end an otherwise decent series (and legacy) on a bad note?? Bah!
Diagnosis:
"slapped together"