For landscape photography most people have used a lens in the range of 24-35mm with film. With a 1.5 crop camera that would mean a 18/20/24mm primes. Of these the 18 and 20mm are no better than a modern zoom lens. The old thinking regarding primes was true when zoom lenses were designed with a slide rule. With the dawn of computers to design optics zooms have gotten dramatically better.
Please forgive me if this seems picky, but I do not find the wide angle right for most landscapes. In particular, it decreases the grandeur of many mountainous shots because distant mountains look far too small. I prefer normal to short tele for many landscape subjects and like the compressed sense of depth they provide. I even like the look of my 400mm for landscapes sometimes. Much of my work with the Pentax 67 is done with a 105mm (35mm equivalent of about 55-60mm) and then slightly cropped.
Going back to the forbidden ground of the Luddite, one of my current methods of photographing life is the reverse of most: I put on a lens, usually 24mm on D200, and it never comes off until I get home. I was going to remark about my dust experience but have decided not to tempt Fate! There is something freeing about not having to change focal length...
When I was first learning wedding photography, I found changing lenses to be a huge distraction so I learned to shoot weddings with one lens on my 6x7 (my 105). I rarely needed anything wider and really got to know how the lens looked. Now that I use a zoom, that training has more than paid off.
I also studied with a man who refused to carry a meter. He insisted that almost all wedding venues were lit about the same and he had it all memorized so he could move faster and concentrate more on the photograph than equipment. Perhaps a little extreme, but he was right. More training that has paid off.