Point taken. The world has vastly more vanilla folks than LS people. Many vanilla couples have durable and intimate relationships. We are lucky to count some among good friends.
As for houses of worship, we know several LS couples who are devoted to their faiths, attend worship services frequently and so on. Thus we would not estimate any vanilla gathering with a particular representation of vanilla or LS couples.
The original post was a (perhaps clumsy) attempt to explore a different idea, namely that modern life has so glued (many of) us to screens of various sizes and isolated (many of) us from community. We see this in so many young people, often having underdeveloped social skills and retreat to the anonymity of the internet. That is emphatically not an "attack on millenials" but rather a concern for their future marriages and growth as couples.
Part of the calculus of the LS is that couples have to invest in wide open communication and a willingness to work through sometime unpleasant feelings such as envy, jealousy and so on. The conventional wisdom is that the reward for the investment is play. What we were getting at is whether the relationship work that is prerequisite to swinging might have substantial benefits beyond playtime. There are already abundant --and still more accumulating-- data that isolation and loneliness predispose to premature death and other illnesses. We wonder whether the social skills of "dating" in later life, the negotiations that couples go through, the intensities of those experiences make a difference in their happiness --as individuals and as a couple.