Earlier quoted context omitted.
I'm all for experimentation but getting rid of JS in this case almost certainly results in worse performance. You're trading a bit of load time for significantly slower runtime/rendering.
Huh.... why would a CSS animation of a transform be slower than JS? This is strictly for the "CSS transform" case ofc - obviously pure webgl would be way faster. I'm having a hard time seeing it. My experiments with CSS animation have always performed much better in CSS than JS (again, excluding it being pure webgl/canvas JS). And ofc there's the nice bonus that it works if I haven't chosen to trust and whitelist the…
Of course that the animations won't map to all the animations you can manage with js.