> Whether their ideas and worlds stand up to Asimov and company, or happen to be appealing to a particular reader, is another matter, but the command of writing itself is overall better, I'd say.
But that's just the thing -- science fiction is about the ideas, and about the sociological and psychological impact of those ideas.
Whether a work has literary merit is neither here nor there for most people, and "science fiction" as a genre has been looked down upon by literary folks since it's inception. I don't know why anyone would be interested in praise from a community that is so invested in snobbery.
Regardless, science fiction authors of the time did have literary merit, if that's what you care about. LeGuin and Butler, are both regarded well in modern literary circles as far as I know. Vonnegut himself is regarded well also. At the time however, their books were condemned as being inadequate by the prevailing literary reviewers for various reasons unrelated to their actual writing.
Work from that time is perfectly functional and servicable for the most part, especially if you look at the places where the stories were submitted and published -- a small majority of Clarke's works ended up being published in Playboy, I don't think anyone can blame him for not creating a literary masterpiece when the majority of places that would actually pay him for his work were essentially pulp magazines.