The other side of the answer for HTMLite (other specs we write might differ here) is that it explicitly aims to be a more legible alternative the WHATWG spec which better describes the HTML most web developers (like yourself) are writing and most browser engines are implementing. Except ofcourse for the popular few sites and browsers.
Which could be useful documentation today for those who care about e.g. Lynx users. Certainly allowing browsers to specialize to the commandline, voice, etc is a big motivator for me!
Yes, dropping JavaScript made a massive difference to the spec! Which is appropriate to drop anyways because all other browser engines than the big 3 (Gecko/Firefox, WebKit/Safari, and Blink/Chrome) barely support it if at all.
As a carry-on from dropping JavaScript, HTMLite no longer needs to describe how to handle edge cases when altering the DOM. Or even how to expose the DOM to any scripts!
The other main thing is WHATWG’s error recovery algorithm. That gets better support, but in my view isn’t fully used enough to be worth implementing.
HTMLite specifically discourages use of <div>, <span>, and image maps to better cater towards non-visual browsers.
Beyond that, to allow for specialization, HTMLite is currently very lenient towards how webpages are rendered: no element, attribute, or even CSS is described as being required.