Copyright needs to be shorter for a lot of reasons, but one of the main ones would be that if copyright was a reasonable length (15 to 30 years), this would all be a moot point and everyone could use books from within a recent timeframe for any kind of use, including AI training.
Further, this would make it feel a lot less hypocritical like piracy is okay for giant corporations and their products as long as they make oodles of money but piracy for regular people is still bad. I mean for fucks sake they put the guys from The Pirate Bay in prison for less, under the same argument: that they were profiting off of pirated works, just like AI companies are. Yet somehow it's totes okay for OpenAI, Microsoft, Google, Nvidia, Meta, and Twitter, and they're not being sent to prison over it. It really re-enforces the feeling that there's two justice systems, one for the obscenely rich where as long as they make crazy profit they can do whatever the fuck they want, and one for the poor where they get fucked six ways to Sunday for doing on a small, individual level what giant corporations do at industrial scale.
The solution is to fix copyright and make more works public domain and then nobody is going to prison and nobody is getting a free pass over what's considered illegal for others.