While social permissiveness is distinctly a phenomenon of the west
How about Japan or Taiwan? Reminder: Taiwan legalised gay marriage in 2019!
I don't like to use the term "Western" too much. It's more clear to say "modern". Example: Japan is not at all Westernized, nor Taiwan, nor South Korea, but they are definitely modern.
-- Edit --
As a counterpoint, I would say that India (in my limited experience on-the-ground) is way more social conservative than Sri Lanka. I was genuinely surprised by the social permissiveness in Sri Lanka. It was a world apart from India. Thus, I would say Sri Lanka is on-the-cusp of being considered modern (in my eyes).
Everybody in the entire world alive today is in the present. Nobody is more modern than anybody else. An Amish farmer is no less of a modern man than a San Francisco web developer. You are crossing your wires, using temporal language to pass subjective judgment against other ways of life. People who don't live live styles similar to your own aren't living in the past, they are in the present with everybody else.
You're essentially calling everybody else backwards. That's judgemental and subjective, not objective. It's a mentality of cultural imperialism, only one step away from calling for people to be "brought up to speed", e.g. forced into your way of life.
I think we're talking about culturally Western here, not geopolitically Western. I can't see even a (sane) cynic call these 3 countries culturally Western unless you think being a liberal democracy automatically makes you culturally Western. And Japan is one of the countries said to have "Westernized"!
The world is being westernized thanks to the influence of western media and culture. So in that sense, it can seem like “westernization” and “modernity” are the same thing. But the Japanese and Taiwanese also wear western-style business suits, wear jeans, drink coffee, etc. We wouldn’t say that jeans are “modern” rather than being a western influence. Moreover, in other parts of the world you have a resurgent, fundamentalist Islam. In the 1950s, Egyptian women didn’t wear headscarves. Today, most do. That’s also “modern.”
Same-sex marriage also isn’t a good example to gauge whether a culture is socially permissive, because sexual orientation is biologically determined. The scientific fact of that has been critical in acceptance of that in the East: http://olivia.thechiongs.com/2015/03/28/a-purely-practical-v.... It’s more of a social accommodation for a biologically defined group, rather than permissiveness as to individual behavior. That makes it quite distinct from western liberal culture, which I think would say that it doesn’t make a difference whether it’s a choice or not.
I don't like to use the term "Western" too much. It's more clear to say "modern". Example: Japan is not at all Westernized, nor Taiwan, nor South Korea, but they are definitely modern.
-- Edit --
As a counterpoint, I would say that India (in my limited experience on-the-ground) is way more social conservative than Sri Lanka. I was genuinely surprised by the social permissiveness in Sri Lanka. It was a world apart from India. Thus, I would say Sri Lanka is on-the-cusp of being considered modern (in my eyes).