I don't know that all writers considered to be modernists can be associated with obscure language, so I'd cross that criteria from the list. John Dos Passos experimented with form and focused on colloquial language as well as commercial language. Woolf also experimented with form in ways that make her work challenging and new, but her terminology was not really obscure. Hemingway did not use obscure language.
(In fact, Hemingway and Faulkner had a famous, pithy and public disagreement about language.
First, William Faulkner, speaking of Ernest Hemingway: ‘He has never been known to use a word that might send a reader to the dictionary.’
And Hemingway’s response: ‘Poor Faulkner. Does he really think big emotions come from big words?’ http://grumpyoldbookman.blogspot.com/2004/07/faulkner-v-hemingway.html)
Ezra Pound and James Joyce did, however, go out of their way to create difficult and challenging work. The extremity to which they moved in this direction could be call for some criticism, though many will also say that this is call for praise.
The strongest argument against using modernism as a standard for use in judging literature at large, it seems to me, is the same argument we'd use to suggest that no single movement is capable or adequate to use as a standard. Times change. Writing changes. Without getting better or worse, art changes.
You may be served best by looking for criticisms of modernism as a movement as opposed to arguing against modernism as a model for judgment.
Another potential knock on modernism, to generalize, could be the emphasis on experimentation. Originality is prized for good reason, but experimenting is only valuable is so far as it is engaging and interesting; in so far as it serves the art and facilitates actual expression.