For me it's about the fact that html was designed for documents with minimal interactivity, and while it's possible to represent a highly interactive application in html, it poses several significant headaches for developers.

I don't know the right solution, but it's clear that what we have right now doesn't suit our needs and make web development far costlier than it otherwise could be.

Indeed. We all know hiccup[0] style is the one true way to do it.

[0] https://github.com/weavejester/hiccup

Could've sworn we just did this: https://news.ycombinator.com/item?id=29093482

Especially when it doesn't seem to bring anything over haml and pug.

The most concise and precise way to write a language is generally in the language itself too.

Doesn't really apply to HTML.

Using indentation instead of XML-like opening and closing tags is way more concise, and encodes exactly the same information.

It's shorter, I don't know about concise though I suppose that's a subjective point anyways. While it's generally exactly the same there are some corner cases involving formatting rather than structure tags where it's not always 1:1.