My point was "less money goes into book in general -> we'll have less books".
You're right that there are other factors at play here, which are all intermingled. For example:
* It's easier to produce content now, bringing down costs.
* It's easier to reach a wide audience. Both because of the internet, and because people have more time to spend on content.
* Technological changes may make many new ways of making money, etc, and in general just change things.
...
Still, at the end of the day, an author has to sit down and write for 1000s of hours to make a book, and to do this over and over again to make a good book. If people can't make money from this pursuit, less people will be able to do it. Maybe in a few decades, there'll be other ways to get compensation for these pursuits that has nothing to do with copyright. I still think the mistake is to think only of the Disney's of the world without considering the tiny indie studios, the small-time authors, who barely manage to get by today. They must be a part of this conversation as well.