OP here. Thanks all for chiming in. Interesting that some read the sex scenes as comedy. That wasn't how I read them, but now that you mention it, I can see the argument (and maybe they work better that way.)
I also appreciated her characterization of her kid's childhood as a period of time she spent making so many sandwiches that her child was likely to remember as some vague fugue-state. That definitely resonated with me.
Overall, I'm surprised to see this book last on so many "year's bests" lists. My pet theory is that the editors at places like the NY Times just reward the buzzy books with those lists. (Reading the Times review -- gift link here
https://www.nytimes.com/2024/05/12/books/review/all-fours-miranda-july.html?unlocked_article_code=1.mU4.Pfay.nMeVzrqeT-BY&smid=url-share --, it was not entirely clear to me that the reviewer enjoyed the book. I work in culture/media and I am familiar with how reviewers sometimes talk about or around a piece of work that they feel is too "important" to pan.)