Most libraries that people have access to are more like "Disney+ for books". They have a limited selection of extremely mainstream books. If you're happy to make do with whatever they have on offer then you're fine, but if you want something specific you'll have to go out and buy it.
Back in the DVD days and before everyone broke ranks and tried to start their own service, the thing that made Netflix great was that no matter what you wanted they had it. Having no retail footprint meant they could stock everything without having to compromise. Libraries don't have that advantage.
This is also one of the areas in which the Internet has actually delivered on early promise (though the success has been a long time coming, and remains precarious): the Internet Archive offers access to over 20 million records, and aims to have a web page for every book ever published. Note that this still isn't full access to all material, but it's quite good.
The US Library of Congress has also been expanding its public access, as have other large public libraries (the New York Public Library notably). LoC also have specific programmes aimed at disabled readers such as its NLS BARD programme for the visually- and reading-disabled.