The underlying problem isn't PDF, but the fact that HTML is still completely unsuited for long-form content. Really basic stuff like a proper markup-based TOC i

The underlying problem isn't PDF, but the fact that HTML is still completely unsuited for long-form content. Really basic stuff like a proper markup-based TOC isn't a thing in a HTML. And on the browser side there are just as much problems, you can't bookmark your scroll position and basic scrollbars are a terrible user interface for long HTML content anyway. There are other really basic problems like not being able to link arbitrary HTML content unless the author of the HTML put an anchor in the document. ePub, mobi and such were developed to work around those limitation and make more usable book formats, but no web browser has native support for them (Edge had some support, not sure if that still there after the Chrome switch). Despite being HTML-based, those formats aren't really part of the WWW. PDF does what PDF was designed to quite well, it's virtual paper. But the WWW has kind of failed to evolve into becoming a platform where you can publish long-form documents on, so PDF still continues to dominate.