We already do lots of rendering to cached images. It's not a panacea. It saves you from unnecessary recomputing. But many actions update the rendered state per-frame. Zooming is a great example. You can't cache it at every resolution.

Maybe there's a way and we didn't find it? We looked at every example we could find. There's a lot of canvas apps without WebGL. But they're all orders of magnitude behind the Figma benchmark. Everything not using WebGL felt noticeably less smooth.

And in our user testing, our texting editing is already past the valley :)