We definitely use video as a learning and analysis tool at the lower levels, but a simple video camera (even an inexpensive flip video version) with zoom, slomo and replay features suffices for lesson reviews.
Dartfish is really expensive to implement, so it's not as widespread as one might think. At a lot of rinks, there are one or two coaches who provide the service for a fee, so it's not as if every coach buys the hardware and software for Dartfish.
I don't really see "How To" videos replacing live skating instruction. A video can tell you how that person teaches/performs the element, but it can't look at the skater attempting elements and say "you're dropping your shoulder, the free leg isn't behind you, that arm position isn't working; let's change it to prerotated."
Video review is one-way communication. Live instructors provide two-way conversations since they answer questions and provide specific feedback.
There are online "distance coaching" services such as
www.mysk8coach.com. I'm not sure about the timeliness of the feedback since I don't know anyone who uses those sites. For a lower-level skater, it might be best to get the immediate feedback that a private coach provides during a lesson.