Disagree. Deprecating things like <frameset> will not make it easier to build new browsers. Shadow DOM and WebComponents are significantly more complicated for browsers to implement than any old "deprecated" technologies. If you don't want Chrome forever, what you want is not removing old technologies, it's preventing more new technologies from becoming a part of the web platform.

We'll get better at building software. Even with huge engineering teams, we can only build the browsers that we have today due to improvements in large-scale software engineering.

Keep your eye out for Ladybird Browser and Servo.