Alan Kay is a huge proponent of capital P Personal Computing. Meaning that anyone should be able to edit programs, edit how text gets displayed on your screen, etc.

HTML is a language to structure text with, that's perfectly fine to him. The problem is that the browser decides what that text should look like to you. Not only its aesthetics, but also how and where it gets displayed. If you want to visit webpages in a painting program ro find images, why not?

This makes a lot more sense if you watch one of his smalltalk demos, he draws a wheel and a car in a paint-like program, then tells the car to rotate as much as the wheel is rotated. He can rotate the wheel with his mouse.

Then he paints a pedal, and if clicked on it accelerates the car etc...

This is not a programming environment, but an operatjng system, you're free to make all your programs do everything

Every webpage you view nowadays is at least written in HTML, including this one you're reading, mostly it also includes Javascript and CSS.