I’ve often wondered the same thing. Not only is there little constructive criticism of landscape architecture, most landscape “enhancements” are considered good decoration. It seems that it matters little if it is viable, sustainable or possessing of any design integrity–if it’s pretty, then it’s pretty good.
The reality is that there is an awful lot of awful design out there. Some of it mandated by city landscape codes so specific as to restrict any creativity. Others are destroyed by common maintenance practices after the landscape architect has relinquished control–nandina is box cut, trees have forced minimum spacing and have you ever tried to let a podocarpus grow into the tree it was meant to be (?).
People still think landscape architecture is an unnecessary extravagance they can do themselves. After 27 years in the profession, I’m still asked about spots on roses and mowing techniques or roof angles and window types. I am neither landscaper nor architect, but many still only understand one of those words at a time. Cable TV has helped a lot with making Landscape Architecture more visible, but even there, I constantly see poor examples of design or, even worse, poor examples of landscape architecture created by non-landscape architects. This does nothing to help our cause.
We’re shooting ourselves in both feet when we praise landscape architecture just for being. We need to separate the good and the bad and thereby educate the masses as to who and what we really are. Until we recognize and admit our own fallibility, we will never grow into the authority we should be.