Today's CSS - if anyone would take the time to actually learn it as they do JavaScript - doesn't need something like Tailwind to make it powerful, scalable and manageable.
I write plain CSS today, which is then scoped to components or bundles of interactivity, and all of those point to major, top-level control sheets that help determine the mode (light/dark/high contrast) and the theme. We tweak small changes up high to effect large platform changes throughout, saving time, energy and headache of the hunt/peck exercise.
I don't understand the statement "no one is going back to writing plain CSS" because plain CSS today _is complex_. It is a beast. But it is still "plain" CSS. Yes, it has evolved, it has grown, and it meets today's modern needs with excellent results.
CSS nesting is coming up soon: https://caniuse.com/css-nesting That will more than likely allow me to migrate any projects I have with Sass still in play, to remove Sass. One more dependency removed. Done.
So there's really no need for Tailwind if you know how to build with modern CSS - with the one caveat that if a project _already_ has Tailwind in it, it is a bear to work with/alongside.
That to me is the biggest con with Tailwind: it gets in your way when you don't need it.