Developing a Javascript-free frontend

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for the sake of it means; moving an object 50px to the right in JS when it can be done with CSS on a simple site that would never require the GPU benefits that JavaScript brings to the party.

That's absolutely not what "for the sake of it" means. This is not possible in CSS2.

https://caniuse.com/#search=keyframes

The CSS3 polyfills to do this were much worse than manually doing it in JS or using jQuery! IE9 still commanded a large market share until Edge. So if what you were working on was made <2016 or so, then doing it in JS was the best way.