If you don't mind spoilers you can read more here:
https://www.dcurbanmom.com/jforum/posts/list/1248246.page
But OP I was in your camp, I gave up near 100 pages in. You described what I disliked about it really well. "The sex parts were like a teenager trying to imagine being old" is exactly it.
I'm convinced the venn diagram covering the women who found this book empowering and deep and who are also fans of Glennon Doyle is complete circle.