As an artist can use a guitar instead of their own mouth. But can an artist's art be the guitar playing itself... hm.

Absolutely it can. Numerous artists have created work that unfolds itself into something beautiful through their planning but not through their power.

But can choosing a book from a library be art?

Choosing a urinal counts as art. Of course choosing a book can.

The argument here hinges on the definitions of inherently vague words.

Art is an inherently vague word.

I would rather watch one made by people who care.

This right here is the crux of my argument. What about art made by people who care, but made with ai? Is it so impossible that people might care about something and use ai to make it?

I absolutely do not contend that using ai makes something art. I merely contend that using ai (even as a major part of a work) is not sufficient to make it not art. To whit,

Joel Haver uses an AI filter to do his rotoscoping. I like Joel Haver just fine.

It sounds like you agree with me on that, at least in principle.