Defending against bare handed opponents is pretty basic stuff in any martial art I've ever studied, you are correct there and I bow to that wisdom respectfully.
When you are not armed and your opponent is also not armed you only have to learn to defend against their hands, feet, arms, legs, heads, shoulders, elbows, knees, things that can hurt you but not cut you or that are generally able to bludgeon you to death with one blow (I know, some people can, MOST however cannot).
So this is basic stuff. This is the first defense type most every martial artist learns.
However, when defending against someone with a weapon, most especially when you do not have one, these would certainly appear to be more advanced techniques to me.
These types of techniques take a long time to learn, much less perfect, in every style of martial art I have ever made a study of or have heard of in my time. It takes many months of practice to learn how to handle yourself in a fashion that will lead to walking away from such an encounter in one piece. And you must learn different techniques for each type of weapon you are facing, so each weapon type you wish to defend against will take you more time and require a much greater effort than the more "basic" techniques of defense against an unarmed opponent would.
You do not use the same techniques to defend against an attacker with a knife that you use to defend against an attacker with a baseball bat, do you? So even if you consider defending against someone with a baseball bat a "basic" defensive technique, it is still a more advanced, or more difficult if you prefer, methodology than the techniques employed against an unarmed opponent.
Consider an unarmed first year student, regardless of his style, attempting to defend against someone who is weilding a Manchu broadsword. Do you think that student would consider this type of defense as "basic"?
It would almost certainly take someone with a much greater level of skill to come out on top in such an encounter.
I have studied martial arts for over twenty years, a few different styles, I have even studied the Manchu broadsword as a weapon type both offensively and defensively, rather extensively. I can tell you without question in my mind that to this day I would not consider this scenario as anything less than an "advanced" art, because even with the knowledge and practice that I have doing that exact kind of thing I could still not be certain that I would prevail unarmed against my opponent.
Therefore, these types of techniques do not seem to fit into the "basic" category by any definition that I know of.
They would appear to be demonstrably more "advanced" in that they take more time, more skill and greater effort to learn and then to perfect.
I have heard weapons called "the great equalizers", because they turn a relatively easy to handle, unarmed opponent into one who is much more deadly for anyone to face.
I am puzzled as to why you would consider facing armed opponents not "advanced" compared to unarmed opponents, regardless of style or technique.
Perhaps I am wrong, I have been before and am willing to admit I may be again.
Maybe you would be kind enough to educate me?