Why is Heinlein so revered in the scifi world?

I have been taking a tour through famous scifi and I cant figure out why Heinlein is so revered. His books are frankly very difficult for me to get through. Most of them have very long pedantic sections that rival Atlas Shrugged in detailing the story to give a philosophy lecture. Was it his innovative ideas or do people really enjoy a 40 page ethics lesson in a book about space marines or a half book about interstellar commerce following a first half of space adventure?