Please find me an example of McCaffrey being criticized for releasing the same stuff over and over again. My point was, she's released a ton of books, yet they're highly varied and of a high quality, too. And considering you've confessed to never reading any of her stuff, you're not exactly in a place to dispute that assessment =P

(Though admittedly it's all a matter of opinion in the end.)

The single biggest complaint against McCaffrey is that she somehow "betrayed her roots" by taking the decided fantasy-driven Pern series in a much more sci-fi direction, but that's really a matter of taste. I get why it bothered some people, and quite honestly it was jarring to me at first, but I'm pretty content with it now.