I agree with a lot of things said in this video, however
in my experience, mostly, when the instructor is not good, or lacks certain knowledge, or simply doesn't teach something even though he knows it, I have found that you need to resort to learn some things by yourself.
When the martial arts instructor has 50 other students in the same class, there's a lot lot of things he won't teach you, he doesn't have the time to see everyone of his students and give personal advice.
He might see some things and correct them, and there's a lot more he will miss.
Also, he won't take the time to teach you the techniques properly, because he has a lot of other students that are more advanced, so he won't start teaching the mechanics of how to throw a punch, how to throw a kick all over again to 30 other students who have already been practicing poor technique for months, and the ones who have good technique are the ones who started to train years earlier when the martial arts gym wasn't that big, and you have to learn that stuff elsewhere.
Even when there's less students, like ten, a lot of times the instructors don't take, the time, I have had some who do, and others who don't.
Usually the ones who do are the ones who have fewer students, but not always.
And with the ones who have 50 students in each class, and they give like 5 classes a day, you end up learning from students, instead of the master, because, again, he doesn't have the time to teach everyone, he's busy doing something else.
So I see online lessons, or DVD instructionals as valuable tools for supplementing instruction from a live master, or sometimes even replacing it.
But there's no replacement for a GREAT teacher, who takes the time, is patient, really knows what he's doing and knows how to really teach.
But not everybody is like that.
Also like an analogy, like playing the guitar , you want to learn a certain song, there's a lot of songs your teacher has already told you, but you can't expect the teacher to teach you every single song you want to learn, you need to have the capacity to learn the songs by yourself, either by picking them up by ear or by music sheet, but in order to do that you need to have experience and develop that capacity to do it every time faster and faster.