Backwards compatiblity is not the issue, it's the forwards compatibility that is the issue. The entire evolution of HTML is based on forward compatibility and progressive enhancement.
Many modern HTML features exist because old parsers were extremely forgiving or even buggy. Even something as simple as the HTML5 doctype isn't a valid SGML doctype expected by HTML 4 browsers. It is a hack which just happens to produce the correct results on older browsers.
Javascript used to have to be placed in HTML comments so that old browsers wouldn't display the source code as content because the earliest browsers had no concept of client side scripting.
Obviously a frozen platform is better to work on -- that's why people continually suggest such things for HTML. Make it compiled! Make it binary! The current situation is far from ideal. But if someone had done that with HTML 1.0 it would have been a lot harder to make it version 5.0.
Many modern HTML features exist because old parsers were extremely forgiving or even buggy. Even something as simple as the HTML5 doctype isn't a valid SGML doctype expected by HTML 4 browsers. It is a hack which just happens to produce the correct results on older browsers.
Javascript used to have to be placed in HTML comments so that old browsers wouldn't display the source code as content because the earliest browsers had no concept of client side scripting.
Obviously a frozen platform is better to work on -- that's why people continually suggest such things for HTML. Make it compiled! Make it binary! The current situation is far from ideal. But if someone had done that with HTML 1.0 it would have been a lot harder to make it version 5.0.