As others have stated, the reason that video is worse than text for learning is because
A. The rate at which you can read is faster than you can listen
B. Video technology is often a hassle when you need to skip around.
C. It's cheaper to write and revise text than video.
D. Videos consume large amounts of data.
But I'm going to add another point.
E. Lecturers most often don't know what I as a student am struggling with. They may focus on things I understand easily and spend a majority of time discussing things I already know. However, if I decide to skip a portion of a video I could potentially miss a really important detail necessary for understanding the subject matter.
With a book I can skim. Important information is often marked in a certain way to make it stand out from other data. It's also organized in sections and chapters so I can easily skip around. With videos this isn't possible.
Also, what happens when all of this information is outdated? Now you have a bunch of videos with outdated and potentially false information out there and nobody will know.
My ideal alternative would be to remove lectures entirely and to have interactive labs where teachers and TAs help students complete assignments based on assigned readings. The instructor for the course would be responsible for overseeing the teaching assistants and preparing the course outline. The TAs would help guide the students in completing the assignments or mini projects. Then a couple of time a semester there would be larger projects that tie together what the students have learned.