I recommend going with Pollen if you really need some kind of framework for CSS. I believe that's the way to really help with CSS development without the burden of learning yet another layer of abstraction over simple CSS.
Tailwind is not for "people who don't know CSS", it's a design system. A value prop of it is for teams who don't have a dedicated designer. Tailwind gives you a set of fixed "design decisions" in the form of utility classes, which is far more flexible than something like Bootstrap, while still offering set constraints (which brings uniformity).
Your idea of CSS is not simple. It's slow, it doesn't scale well, it's difficult to refactor, and it's a higher level of abstraction than Tailwind.
And why is learning CSS mutually exclusive with learning Tailwind? Tailwind is literally just abbreviated CSS properties and some nice tooling.
Everyone who uses CSS uses a methodology, and that methodology comes with its own abstractions. For example, Tailwind is low abstraction; all you need to learn is how the config works and naming, which is relatively intuitive and can be learned in a day or two. After that you're dealing with mostly straight CSS properties.
Most methodologies people actually use when they implement "vanilla CSS" or SASS impose a high level of abstraction—naming, which classes do what, which classes map to which elements, how the DOM hierarchy must be structured, etc. Just because these things aren't necessarily committed to code anywhere (yikes) doesn't mean there's not a complex abstraction layer.
This is the problem.
Writing good CSS is hard, and is it’s own skill that needs to be learned and developed. Abstracting that out so the non css experts can create consistent interfaces without having to ‘learn css’ is the goal.