[pcwalton]

I don't think this is a reasonable assumption for the browser at all. It's 2021; WebRender has proved that a better design is possible.

[kevingadd]

Sure, but are Chrome and Safari going to do a WebRender-style renderer anytime soon? WebRender is great but in practice it affects at most (generously) 20% of the web audience. Optimize for the browser you have, or maybe the browser coming next year, not the one your customers will have in 5 years.