tailwind removes the abstraction that you don’t need, since many people in react tend towards one scoped css file per component with classes for each element anyway

What abstraction does it remove? In my view, it just adds slightly different abstractions. Instead of knowing an element has a clean block of rules with set meanings, you get a long (potentially grossly formatted/ordered) string of class names that mean the same thing as the CSS properties for the most part, but you've gotta learn a new set of aliases for them. If I am working on someone else's component, one of these scenarios is way easier for me than the other. Even when I worked with TW for a while, I never could really remember a lot of those class names.

csszengarden is cool but I haven’t seen the html/css split help an end user, or really even me as a developer.

You may have never refactored or reskinned a site. I have several times. The hardest projects like that were when content and presentation were tightly coupled. Those felt like pulling teeth to get done. important! every time a dev buried a style tag somewhere deep in some (for all intents and purposes) unchangeable Java code... shudder When they were loosely coupled, it was fun and went much easier.

edit: respect for knowing csszengarden. That site honestly was the first time I learned this principal and saw it applied. I've themed several websites over the years so I've used the concept myself.