I think show versus tell gets harped on so much because it is important, and because it's an area most new writers are lousy at. Tell is important; no novel can be all show and no tell, nor should it be. Tell is an important part of any writing. But there are many places where show is the only proper way to write a scene, whether you're Annie Proulx, Orson Scott Card, or anyone else.
The problem, I think, is that many new writers can't write show. Tell is easy, and scene after scene after scene is written this way, and it kills any story. The writers think they're using show when they're using tell, and it's murder. So show versus tell gets a lot of air time. I don't think the problem is that show versus tell gets too much air time, but that other aspects of writing well get too little.
I'd love to be able to say that beautiful prose is a must, but it obviously isn't, else there wouldn't be so many successful writers who simply do not write beautiful prose. I'd almost go as far as to say most don't. Beautiful prose is something to strive for, but good or bad, right or wrong, I don't think it's why the average reader picks up a novel. Most readers are interested in story and character, with prose coming in a distant third. Readers want competent prose, but darned few care about beautiful prose.
I haven't read Proulx, but I think the above, and your description of flowery prose for its own sake in the abstract, is right on the money.
-Jason