Well, to each his own. People certainly will shoot only what interests them, and I guess that's true for all of us. Same for what grabs us as viewers; Some types of images do it for us and others don't, and I suppose that can extend to entire genres.
That said, there's certainly a market for landscapes, as there is a market for all genres, and it seems that most people can be grabbed by a well done landscape, even if it's been done before, even if it's been "done to death". Millions of people every year buy postcards and calendars and prints and posters of landscapes because viewing them grabs them in some way, and that includes all the ones that have already been "done to death". People know who Adams is because his images still sell to people who find those images inspiring in some way, so they hang them on walls, put them on desk calendars, computer screen wallpapers, and all the rest of it.
If you've never stood in front of a Peter Lik print that's 4 or 5 feet wide, you may not get the full impact of what a well-made landscape can do to your senses. Likewise, if you've never actually been to Yosemite or the Grand Canyon or the dozens of other famous places that have been "shot to death", you may not get why people can't help themselves when they're standing there engulfed in a landscape that has so much impact on the senses, and you should probably get out more and go to to those places to get a better understanding of the dynamic that drives the photographers who shoot this stuff, and the people who appreciate it.
As for copycats, that can be said of every genre. Why shoot portraits with the lights arranged in one of the dozen "classic" ways that's already been done a million times? Why pose your model the same way it's been done a billion times already? In fact, you probably use the same poses and lighting over and over and over, not caring or worried at all that it's been "done to death". You think it's really all that unique that you stick a different face in the shot each time, while using the same poses and lighting and focal lengths and DOFs from session to session to session?
A billion school head shots are identical in terms of lighting and pose and "cheese" smiles and cropping, and yet every year we get a millions more of the same. Corporate head shots, same thing. Glamour magazine covers have about a dozen different looks, repeated millions of times.
Still lifes, water drips, bug macros, birds on branches, seagulls in flight, every animal you've ever heard of, flowers in bloom against black velvet, sunrises and sunsets in every conceivable configuration with water or rock or grass or a barn or a couple or a lonely person, and a million more themes - done to death. Pregnant woman holding her belly, ring in a Bible with heart shadow, muscled man holding a baby, homeless people laying in the street - all done a million times already. And so on with a million more themes. "Oh, how boring", says the elite "tog" with his nose in the air, "how utterly banal".
Taken to it's logical conclusion then, if you can't shoot something that's NEVER been shot before, you're just a copycat, so why even have a camera at all?
I don't hold to such pretentious, extremist, egotistical points of view. Those who do are welcome to them, but I have little respect for such opinions, personally. I will shoot whatever catches my eye or stimulates my senses, even if it's been done a million times. And then I will share it with others, some of whom will enjoy and appreciate it on some level, some so much that they will buy it even, while others will find it boring and banal and not worth the time it took them to glance at it, and that's fine too.