CSS grid? No. Web Components? No. WebAssembly? Fuck no. Everything that isn't simple HTML and CSS... no.
Stop over complicating things. Text should be text. Not gray throbbing placeholder bars.
Images should be images, not executable code.
Video codecs should not depend on hardware acceleration that has only been in hardware for a few years.
And if your browser can't display HTTP sites that means it's broken. Get a new one not controlled by mega-corps and their invalid profit-motive PKI assumptions.