Part of what's dumb about threshold is the idea that one little isolated ship is somehow on the cutting edge of engine development. That kind of thing takes large research institutes with resources and experts on hand. Not a bunch of officers more worried about keeping their own systems running and dodging Kazon attacks.
ok, that's a nerd complaint that's rather overshadowed by the ridiculousness of "Paris does warp 10 which turns him into giant newt, then gets Janeway turned into a newt and they have newt babies". Which is the worst sounding sounding premise since "beverly crusher has sex with a ghost that lives in a candle".