I really think it's modern American values (or more generally those of WEIRD[1] countries) that are the outlier, when we consider what's "extreme".
Like, I get this whiff of parochialism, like people have never been outside North America or Western Europe.
A concern with ancestors and descendants is baked deeply into many "pre-" monotheistic religions, whether aboriginal, Shinto, "pagan" from e.g. Europe (e.g. origins of All Souls Day), etc. In a way these "different" religions all share much in common. I'm sort-of trying to break down the mental walls we put between these categories. I'm saying these are the normal beliefs people have had since forever.
Likewise, taboos against divorce are ubiquitous. That's like the whole point of marriage. You might not ban divorce outright, but it's supposed to be the exception.
Heteronormativity (which you mentioned) varies more across cultures, but even here I think 2020 leftish culture is now an outlier. Yes, the conservative American culture it was born in reaction against was, in global terms, not among the most tolerant. But while a larger degree of toleration (e.g. via various "third gender" concepts) exists elsewhere, I think this is done in more of a pluralistic/subculture way than by really changing prevailing dominant norms. More of a "oh yeah, some people are different, which is ok, they're called _______." There's also more "you're probably going to form a heterosexual marriage and have kids, but maybe you also had a same-sex lover (especially when you were younger)", like the ancient Greeks. Like, Zeus took male lovers but was married to Hera and seems pretty culturally "straight". I'm saying there may be more tolerance but it still fits into a traditional and somewhat heteronormative framework.
Back on the ancestors/descendants thing -- I find the conflict between leftish and conservative-Christian values funny, because it was Christianity (and monotheism more generally) that did a lot of the work of reducing emphasis on family, lineage, and kin. You could call this the transition from "these are my people" to "we are all children of God". Now we have a leftish monotheism-without-God.
It's hard for me to explain what I'm trying to get across. It's like -- most of the world, and most of history, is conservative/traditional in a way that The Culture (in the Ian Banks sense) isn't. It's focused on kinship and rooted in biological interest. And even when those cultures seem "more tolerant" it's still within some traditional framework that keeps an emphasis on the heterosexual reproductive union.
All of which is to widen the frame and make us reconsider what is "extreme".
I'm also saying that this word "modern" just, with a sweep of the hand, dismisses the traditional beliefs of ... basically anyone who immigrates to America. It's a cultural erasure. Which I think many people will come to regret.
[1] "western, educated, industrialized, rich and democratic" -- a term from psychology