I do value video lessons. In my university i used this method a lot. Whenever i could not understand the teacher's explanation due to several factors (Poor explanation or maybe there were too many students trying to talk to the teacher) i turned to YouTube. In fact i can say for sure that i only passed some tests due to You tube lessons. Nowadays students have access to lots of sources of information and it is much easier to study and do well. You tube and Google are just two examples of that.
I find it very useful, I find that it's easier for me to understand something through a video or image. I've read somewhere that the human mind finds it easier to process images/videos rather than just texts (this is why sometimes we know we've seen/met someone before, but we often couldn't remember their name). But if I had the option to have an actual live teacher, I would choose that any day rather than a pre-recorded video that's already available for the masses.
I totally agree. Learning from good youtubers and other platforms like udemy, lynda etc. where video tutorials and guides are available is a blessing now and I feel we are lucky to have these, whenever I don't understand a topic, I go to youtube or google and find tons to tuts explaining the topic, hence making it very easy for us to learn and comprehend the topic of interest.
It largely depends on the type of video and the technique used by the person providing the lesson.
Even though it's a tool that is much more accessible to us whenever we might need it, I don't think it's that different from old-fashioned classes. I'll explain myself; both in normal classes and video lessons the technique and style of the professor/facilitator is largely influential. A boring, lackluster, less-than-average facilitator will turn an incredibly useful weapon like online classes into a snore fest that will only make you lose your time.
Likewise, we must be careful when picking videos, because the internet is easily accessible for everyone, even so-called professors that lack basic understanding of the topic they are explaining and will only confuse us even further.
I think YouTube lessons are incredibly useful for math and subjects related to it. However, though, they often are not enough. In that case, direct tutoring is needed by either the teacher or tutors at the school. For instance, I had a calculus-based probability and statistics class and finding videos for it was a nightmare.