I don't disagree that Libby's UX for search/catalog is not great (and I'm with you on searching across libraries, but fwiw I find tags fine), but it's light years ahead of the competition for playback.

I treat audible as a last resort not because I want to avoid amazon or because I'm cheap (although both are true), but because it's so frustrating to use the app to, you know, listen to books.