We tried all that stuff in the early 2010s. I was there. It didn't work.

People ditched element-based CSS for good reasons: it forces you to maintain increasingly complex stylesheets, because you end up having to come up with increasingly arcane rules describing how the design links back to content.

But some design isn't about content. Sometimes you need a button that's centered because it just looks better. There's no semantics or document structure you can point to, to justify that.

(So then you end up with post-hoc mental gymnastics like, "hmm, well, it's the second last button on the page in this one instance, so let's write an :n-selector that only targets the penultimate <button>...")

So having classes lets you keep the look and the meaning orthogonal. Which is especially helpful when you don't have total control over the markup (e.g. most content management systems)