Let me put this way: I am way older than 20 years ago, I grew up in a different cultural zeitgeist. Reading was definitely not niche then. And it was much more widespread and much more in-depth when the dopamine dispensaries of today didn't exist.
You can put it any way you like, but we know that the US book market is about the same size as what it was 20 years ago [1]. So reading decliced as much as book prices increased. Unless you're talking about another country, of course.
That means people still buy books, not that they still read. What percentage of people who bought Atomic Habits got past the first chapter? Completion rate may have been very different 20 years ago.
Maybe it's an American problem? It sure has declined over the years but I was surprised by the amount of people walking around with books while visiting central Europe this year.