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.