I don't agree with your first paragraph. It is confusing. Not work all the time against most or most of the time against all is not good logic, the little I remember about logic. But I think I understand what you are trying to say. Still, unless you can say that everything you try in sparing or actual combat succeeds every time, you aren't presenting a good argument against the techniques in the videos. As to techniques in your art, I think you are short changing your art and yourself. I was taught a knife defense that required I take only about a half step outside the jab to my abdomen while striking down with my same side forearm, then strike the forearm muscle of the knife arm with my other arm. I was capable of doing the technique, but didn't really like it too much, not seeing it as safe as some others. One day I was thinking about it and suddenly realized that if my back were to a wall, that would be one of the best defenses I could use. The point being, we need to think why would a technique be in an art if it wasn't useful, and we just need to think it through against different attacks. I would also point out a couple of other things; knowing what a defense will be makes it easier to successfully attack against. Also for as long as you believe a defense (or attack) will not work for you, it won't. But if you keep practicing and trying to make it work, likely you will find you can make it work, and therefore it will be useful at least in enough circumstances to keep practicing it. I don't recall, but what art do you practice that has "any number" of fantasy moves? Another reason I think you are shortchanging yourself.