The charm and allure of fine art landscape photography lies in the fact that it is based on a reality - a recognizable photographic reality.
This debate is an old one. Here is a quote from the 1895 article Photography, Artistic and Scientific by author Robert Johnson:
“On the subject of retouching photographic negatives, there are a great many conflicting opinions, and a great deal of nonsense has been uttered both for and against this operation; some perfectly competent photographers urging that a photograph is quite incomplete until it has been retouched, others asserting that when a negative leaves the dark room it is quite ready for the printer; that it is bad taste, bad art, and, in fact, a very objectionable thing to interfere with it in any way.....”
I think the question of whether or not to retouch (or "alter") is at heart a stupid discussion. And by 1895 the horse had well and truly bolted.
The first practical form of photography was the daguerreotype (gifted to the world in 1839 by the French government) and established photography as a new way of seeing that was quite unlike the way our eyes worked, and quite unlike the conventions of painters. It founded the various styles of photography and established photography as an art form and demonstrated the basic artistic truth that the photograph is made by the photographer, not by the camera.
(not my words, I've lost the reference).
By 1860 few photographers were still using Daguerre's process. It had been replaced by the wet collodion method discovered by Frederick Scott Archer. A glass plate had to be coated, sensitized, exposed and developed within the span of about fifteen minutes, but it had a faster exposure time, was razor sharp, was much less expensive, and instead of being a one off, a large number of prints could now be made from a single negative. And you didn't get mercury poisoning. (Apart from the 15 minute time limit, its disadvantage was that it was made from guncotton and alcohol or ether. Ether is much heavier than air and would drift along the floor from a leaking bottle until it found a fireplace or candle, at which point it would ignite back and explode the guncotton. There were a lot of deaths.)
Anyway, back on topic. The collodian process and thus the ability to easily reproduce photographs altered people's view of their world. The American president Abraham Lincoln said his election was due to his speech at the Cooper Institute and the photographs of Mathew Brady, Have a look at “General Ulysses. S. Grant on a Horse in front of Troops, circa 1864” at http://izismile.com/2012/02/08/historic_photographs_which_are_known_to_be_altered_13_pics.html
This photograph was not regarded in any way as a “fake”. Within 10 years of being able to mass produce prints, photographers were cutting and pasting in order to tell a story. Different versions were sometimes published to see which the public preferred.
Nowadays, while I agree that if it's art, then anything goes, and we have to judge an image by the final result, where it gets interesting is the point at which we limit our artistic licence to stretch our skills. As Georges Braque, who co-founded cubism with Picasso said, “Out of limited means new forms emerge”.