The thing to remember is that one in fifty people qualifies to be in Mensa, which is not particularly selective or exclusive. This is 2% of the general population, not 2% of, for example, readers of Hacker News. Or 2% of software developers or 2% of people who read more than one book per year.

My experience with Mensa is from 20 years ago with the group in Chicago. I was in my twenties and my guess is that the average age of members was late-fifties. In theory, they were interested in recruiting younger people, in practice they were not interested in changing the activities in a way that would attract younger members, like focusing efforts to solve real-world problems. I felt they were more interested in showcasing depth in various atypical hobbies, or to simply talk about how smart they were. I was never in awe of anyone’s intellect. Pretty much just normal people. I don’t think I came across anyone that was exceptionally accomplished at anything.