I read recently that the reception for Insurrection was actually pretty good back in 1999. The critical reception at least. I do remember most of the newspaper reviews I read were quite complimentary, although the "two-part episode on the big screen" soundbite was thrown around even then as I recall. But talk of the plot, the acting, the direction, the action sequences... it seemed to be relatively well received at the time.
And yet, history holds it in very low regard, usually as one of the worst Trek movies. Certainly Jonathan Frakes and Michael Piller both talked in the years afterwards about how they realised during the test screenings that they just didn't have as good a movie as they'd hoped for. Is it simply one of those films that was critically well received, but the actual audience
(ie. paying customers, or "butts on seats") were indifferent? I seem to recall something very similar was said of Superman Returns