The argument basically boils down that in non-component approach (so not a modern web framework) it is harder to reason if you use tailwind classes. The rest is some serious bikeshedding, imo.

I personally started with atomic CSS framework (that was before Tailwind, we had our own) and it has both ups and downs, but overall it is really nice to use once you learn it, and it is not really hard to do so. It does not do anything to enforce variables, but that's why you need to roll either your own layout primitive components or some classes.