It's worth keeping in mind the purpose of copyright. It's a pragmatic tool to encourage investment in creative work for the benefit of everybody/consumers. We may be entering a time where there's less need to incentivize people to write books. At least not non-fiction books which are simply a collection of existing knowledge presented in an a way that's suitable for human readers. A lot of the value those authors provided can now be done by AI. Yes, the AI trained on their work, but now that it's here, we don't need new non-fiction authors quite as much as we used to.

I wouldn't want to live in a world where technology or general people's wellbeing was held back by obsolete laws that ended up lingering on just to protect undeserving special people at the expense of the rest of society. Remember guilds for tradesmen? They were also a monopoly given by the government to special people. They had their purpose but nowadays we have different ways to keep tradesmen working effectively like license requirements and insurance.

Just to be clear, I think we do still need copyright, but that we might be in a transition period where it has to be redesigned to adapt to AI.

Did they borrow the book? If I learn from a borrowed book is that copyright infringement?