Ehh, in some ways correct, but a little too much attention on HTML/CSS, yes, if we replace it with something else, we’ll need a standardised way of interpreting the nodes and information.
Perhaps more accurately to say, the Tree will still exist, like the DOM Tree / Accessibility Tree, because we will still need to make all kinds of representations of the content to make it accessible.
Sharing thoughts is indeed the goal.
But until we have better brain-computer interfaces, we’ll need to do what we can with our limited inputs/outputs, especially when we are drunk/tired/inattentive or don’t even have them (disabled).
My go to classic for the foundation of sharing thoughts is Bret Victor’s talk on The Humane Representation of thought: https://vimeo.com/115154289 — which I highly recommend