Short Summary of My Opinion:
It is definitely possible to learn some things from a video, even if you are a rank beginner. Generally, the more simpler the movement, the more likely it is possible. Compound movements are not good candidates for transmission this way, and neither are any techniques that require a lot of physical sensitivity and partner feedback such as joint locks.
It should be realized from the start that it is extremely unlikely anyone could learn substantially without a physical teacher; learning from a video cannot even began to compare to training under an expert, and successful students need some type of two-way feedback and correction in place. At the same time, it's illogical to think that a curriculum could not be intelligently designed such that some appropriate topics could be covered mostly through asynchronous learning methods such as video/book. Just because it has not been done traditionally in the past due to barriers like technology or funding or cultural norms, doesn't mean it could not be done successfully with the right people and resources in place.
Not all people would like to learn or teach this way or frankly, would be able to, which is fine.