Have you considered the fact that it is YOUR TASTES and not the author that is the problem here? NO AUTHOR, not matter how wonderful or popular, is going to appeal to everybody. You complain of 'flat characters', but honestly, I think he did enough characterization for his main characters. I don't see what your problem is. The reality is that it is the story that attracted and has kept readers all these years. You clearly have a different expectation on how a writer should present characters. I'm more interested in a story that keeps my attention.
I don't think Asimov was overrated at all - his books sold in the millions and CONTINUE to sell long after his death because readers love his stories. He was also a prolific writer. When you consider that most of his books were individual novels, not part of a series, that says something for his creativity as well. Perhaps a good focus for you would be to find underrated writers.
My suggestion is to go to your Kindle account and request a refund if you haven't passed the time limit yet.
edited to add: If it helps any, I only like a few of Asimov's works. I mostly like the science fiction mag that bears his name. Also, MANY sci fi authors, even current today, replace 'God' with some other epithet. Anne McCaffrey's Pern used terms such as "by The Egg" or other such things to relate to the belief systems of her characters. Believe me, curses and blessings do change, even over the course of only 100 years.