It's interesting that this topic waxed hot and heavy for a few days, then lay there for more than a year, and picked up again. Apparently there is more to say. Myself, having just found this place, hadn't known about it, so I just read the whole thing this morning. Lots of good stuff here.
There are some significant areas which haven't been approached, some very large questions. These could include such ideas as: Why do we do landscapes at all? What does the landscape mean now, and how has that changed? With the current huge issues in the environment, what is landscape art becoming?
Just what landscape art is, and how it has come to us historically probably is important since we have inherited from traditions even though we seldom use that heritage with much awareness. When we do anything, there are underlying assumptions. Most often, we photograph the landscape because we "like" it, or are attracted to specific scenes for reasons we typically don't think much about. We take landscape for granted because it has become for us, within our own time horizons, one of the major accepted forms. We don't question that. Or do you? Tell me if I'm wrong! One side of this assumption was stated in the original post that started this thing off. Is landscape art really one of the oldest forms of art? Most people probably think it is.
I'm a practicing artist, not an art historian, but here are some things I think ought to be part of our awareness as photographers interested in the landscape.
In asia it may be true that landscape is one of the oldest forms, but not so much in the west. At least, in Asia, landscape has been important far longer than it has been in Europe (and extended Europe, such as in the Americas).
Prior to the renaissance in the west, art was generally considered to be about religious subjects; even portraiture came into it kind of backward, by including portraits of the doners (those who paid for the picture) in, or beside the scene. The landscape was typically used as a background for human scenes in one way or another. Often, it looked like Donald Duck would have been right at home there. Until the dawn of the romantic era in the west (nineteenth C), nobody seemed to really care that much about the landscape for landscape's sake. I think it likely that they had to fight with the land so hard just to grow turnips.
Landscape became one, if not the primary focus when the Industrial revolution took people away from the land into the cities and industry. Then, landscape came onto the scene charged with deep, mystical character. If you have read Hawthorne, or Melville, you know about this. This same spirit came through in painting. Take a look at Turner, Constable, and on into Bierstadt, etc. Also, people had (some of them) more money, and wanted to travel. People couldn't get enough of it. They had picnics! They fished for trout with artificial flies! They climbed mountains! These activities would not have been very attractive for anyone much ahead of 1800.
And one more. Prior to the industrial revolution, there was no photography of course, and there weren't many people who practiced art. Art was dependent upon a small market composed of fabulously wealthy and powerful individuals and this market was served by a small community of skilled practitioners. If it were that world now, very few of us would be in the game, and there would be no discussion like this. There may not have been anything like what we call "amateur" art, at all.
Now, I realize that this sort of discussion probably goes well beyond the general scope of these fora, and some people reading this may absolutely hate it. My assumption is that if people have more room available for their minds to grow into, maybe they will go for it. Maybe I'm wrong. I guess I'll find out.