> > Doing only the JS version means you spend the same engineering effort but it doesn't work for as many people
Where did I say it would be the same engineering effort? I explicitly said it's more for the CSS version. In my example, the CSS version is inferior to what the JS library can already do. Creating a spring animation is only one of the things that Framer Motion can do in JS built in. If I did everything in (S)CSS I would basically be re-implementing Framer Motion, which, as I stated, is double the work for <1% of users. Why would I want to re-implement a package when it's already there for me to use? So yes, it "absolutely makes sense" to do everything in JS only.