Which complex parts would you omit? If you omit video playing, you've prevented people from using YouTube and Netflix. If you omit compositing graphics on top

Which complex parts would you omit? If you omit video playing, you've prevented people from using YouTube and Netflix. If you omit compositing graphics on top of this video, you've again prevented YouTube and Netflix from showing UI. If you omit canvas and SVG, fancy modern parallax scrolling sites will not load. If you omit WebGL, another half of modern sites which just use it for a rotating logo won't load. Etc, etc... you really can't release a non-100% feature-full browser these days.