The "high" barrier to entry does act as a filter today, but I should add that in the 1990s, it was considered relatively easy, not so different from using email

The "high" barrier to entry does act as a filter today, but I should add that in the 1990s, it was considered relatively easy, not so different from using email; it's only with the existence of modern social networks that the access steps seem relatively difficult. P.S. For many Usenet groups, you don't need to pay anything to get access.