Maybe I'm going out of a limb here, but wasn't the whole point of CSS to not have to touch the markup when changing the styling? Not trying to talk Tailwind down, I have just missed a lot of the evolution of web design in the past 15 or so years.
The most magical moment for me when I started using Tailwind was realizing you can simply cut-and-paste an arbitrary block of HTML from one place to another and have it just render exactly as you'd expect. You don't have to additionally copy-paste a block of CSS, and then fudge around with the selectors because in the previous place it expected to be in some parent container or what have you.
The content will be inserted from an API or with a templating system.
since that is not the case, tail wind is great, even the biggest complaint about tailwind, bloated html size seems like something you can just compile away.
This is, of course, XSLT, which was supposed to take over the web at one point.
I sort of liked it at first. I even added the opportunity for my users to modify the CSS to add new styles, and share these to other members of the community via a configuration page. It was a neat thing but not many people bothered and in the end it made everything more complicated (and I guess I was really scared of vulnerabilities the whole time, what can go wrong with letting your users set the stylesheet.)
Worse, I think this new approach broke the web as it was: an explosion of flash-layout or photoshop--or-fireworks-cut-layout websites. It used to be beautiful. Now the web is just a series of websites styled by CSS. It's sad.
phones (and their screen size + apple killing flash) really killed the beauty of the web IMO. Now everything's an app.
Given that, the separation becomes more of a pointless burden than actually doing anything useful.
We're not living in that future.
But the CSS ecosystem is still useful, and still adapting to our needs today. Tailwind might be considered one of those adaptations.