The worst example is the slipstream drive. In Course Oblivion the alt crew was able to make the slipstream work so why didn't the real crew? Did they just give up?
Janeway-"Oh it doesn't work? Well that's too bad you better scrap it then, keep scanning for worm holes Mr Kim"
Well to be fair, the alternate crew in Course Oblivion was using an "enhanced warp driveď, it wasn't slipstream drive.