Does anyone know how much of libraries' out-of-copyright content, including rare books, is now available online? A tiny fraction? The important stuff? Speaking

Does anyone know how much of libraries' out-of-copyright content, including rare books, is now available online? A tiny fraction? The important stuff? Speaking more generally, despite the promise of the Internet it seems like the more valuable knowledge is inaccessible to the public - knowledge in books and scientific journals. The public is left with the dregs. People complain about how easily bad information and deliberate misinformation spread and are accepted. In the context of my point above, is that a surprise? Remember the old saying about management and accounting systems or really any application: GIGO: Garbage in, garbage out.