I think it’s great when people can eliminate tools that they no longer need, and some projects might not require both server- and client-side variables. Wonderful! But it’s too simple to assume that means they are identical, and one simply replaces the other. There will always be use-cases for some design logic to happen server-side, and some to happen client-side—even if we get to the point where the languages provide essentially the same features. Pre-processors are with us for the long term.
I was Interviewed by Rachel Andrew for the web.dev Designcember (and finally got around to posting a link here)