As someone who made a competing product along these lines (that got no attention or traction): Tailwind gives CSS a "place" in the codebase. It benefits orgs, not necessarily apps. I didn't get it at first either. But it's very useful to the people to whom it's useful.

In my experience, the main problem it solves is the fact that styling in react is still a pain in the butt.

Rails is a fully formed opinion on how you should write a web app in Ruby and all the various technical components you need to fully realize that opinion.

Tailwind is a fully formed opinion on how to use CSS (utility classes etc.) and all the various technical components you need to fully realize that opinion.

Thinking of Tailwind as just a bunch of regular CSS utility components is misunderstanding the scope of the project. That alone has a lot of tradeoffs and compromises - the file size is absurd and you can't bundle things into components, you also can't have arbitrary values in the utility classes. It wouldn't be a complete opinion on 'the best way to use utility classes', or however you want to frame Tailwind.