So I was talking to @gewt about Job: A Comedy of Justice and I came up with a theory that I think explains why Heinlein's late-period work is so kinda-terrible and why I still enjoy it so much
So Heinlein had always been very interesting in the short parts of his novels, like the little snippets inside chapters. He had a very fun writing style, and wrote some fun dialogue with fun characters, right?>
It probably comes from how much of his early stuff was short fiction
And I think what happened with a lot of his longer works is that he'd just start writing fun bits and hope it would end up going somewhere or having a bigger plot by the end. like eventually he'd figure out where this was going, then go back and rewrite it into a cohesive whole
and I'm sure he had editors that'd help this process. No editor would let you publish something as rambly and changing-gears-every-other-chapter as The Number Of The Beast, for example... unless you were God-King Of Science Fiction 1980s Robert Heinlein.
so basically I think what happened is that by the 80s (when he was in his seventies!!) he lost the drive to go back and rewrite and he was too Untouchable for editors to make him.