It seems there are two types of famous writers, and I'll begin by saying I admire both types. One type finds something that works for them and then repeats it. I've heard a few admit that it's tough to come up with new stuff after the third or fourth book, but the good ones do it. Mediocre writers' work may bore some readers after while, but there seem to be enough who don't get bored to make the repetition profitable.
The other type of writer tries for something different each time. They may do stand-alones rather than series. They may invent new characters who take readers in a new direction. Sadly, some authors seem to be so afraid of becoming predictable that they go a little weird, writing stuff that makes the reader go, "Huh?"
I've been reading one of those. This author wrote two brilliant books a couple of decades ago, maybe ten years apart. He made a big name for himself with the first one and followed up brilliantly with the second. Much later comes the one I just put down unfinished. It's obscure, unhappy, and unfocused, and I just didn't care what happened, even though I loved his protag and wanted to know what he's been up to. This book had too many characters and too much angst without explanation. I was very disappointed.
Maybe some people only have one or two worthwhile stories to tell. Or maybe they try too hard not to write as they did before. You've heard the semi-literate saying, "Dance with the guy that brung you." If I had enough fame that I could publish whatever I wanted, I'd try to remember that saying. One need only look at popular actors to see the comparison. Some can play any type of part brilliantly; some must stick to their type. Both may become famous, but we've all seen the disastrous consequences when an actor steps outside his scope (in my opinion, Richard Gere as the sleazy lawyer in CHICAGO). People buy an author's second, third, and fourth books because they liked the first. No one wants to be a carbon-copy writer, I get that. But trying too hard to write something different can result in a mess. And a bunch of disappointed readers.