[rvense]

> I don't see how single page apps invalidate the base concept of separating data, structure, and styling into separate layers, regardless of the format or code language of those layers.

It does not. But using utility-first frameworks like Tailwind doesn't mean you're not separating things. It just means you're not separating things in CSS files. You have the Tailwind setup (which allows you to customize colours, spacings, etc.) and the functionality of whatever component framework you're using. The point is that in the context of SPAs, "styling" (visual presentation) is not limited to CSS.