That said, I still enjoy his works by and large. Somewhere around here I have a copy of his very first novel, which was not published until after his passing. I think this is mainly because it really wasn't very good at all- which is hardly surprising given how young and inexperienced he was when it wrote it. I can't recall the name right now unfortunately.The interesting thing about it though, is that it had a lot of the elements that he incorporated into and expanded upon in his later works, such as the rolling roads and all that stuff. It was cool seeing these ideas in their infancy.
Mr. Buckley talked about his discomfort and embarrassment as he wrote what I recall as two sex scenes for the novel, which (in the above mentioned article) he explained he was forced to add by his editor, who basically told him that he must include some "racy" material if he wanted his book to be published at all.
It is possible, I suppose, that Heinlein encountered a similar demand by his publisher in the early 1970s; by then he was an older man, and may have had to struggle to be taken seriously by any publisher, and forced to deal with commercial and market forces that were extant at that time.
Famous authors have to deal with market forces too, just like everyone else. In the early 1970s, science fiction was at a nadir, the Apollo program was coming under political pressure and would soon be dropped, and ecology and anti-technology themes were ascendant in popular culture. Remember the (rather crummy) SF movie Silent Running, that came out in 1972, which was really a post-industrial dystopian ecology story set in space.