Jon, some "authors" simply aren't very good. I think the only practical approach is to read a chapter or two of someone's work, and, if you find it unacceptable for any reason, just scratch that author off your reading list. There are plenty of authors at GA who do very well in every aspect of their story telling.
If you find an author who seems to have a good story to tell, but has some grammatical issues, you may want to consider offering your services to edit or proofread his work. There are a number of people who do that for GA authors, and it improves the overall quality of the stories. I am totally with you on one thing. I do some proofreading for several authors, but before I volunteer to help anyone, I make sure I am familiar with his earlier writing. If he can't put together two consecutive comprehensible sentences, I'll never offer to help him. Life's too short for that.
So, I would suggest that you help the good, new authors you come across, making use of your love for English and encouraging those authors.