I think the problems Tailwind is facing are a perfect confluence of factors. CSS in general has gotten a lot better over the last several years; you need way less detailed knowledge to implement a visual design than you used to. The CSS spec is also very well-documented, and there's basically infinity CSS out there for models to train on.
Tailwind's value proposition is that they make it easier to implement a consistent-looking visual style without writing a bunch of CSS; in particular, they handle the tricky parts of layout and save you a lot of typing.
But if CSS is good enough that the tricky parts of layout aren't really that tricky, and AI agents will handle the typing for you... the role Tailwind fills is just way less important in the web development ecosystem. Tailwind is great! It's also a big dependency!
Similarly: I think AI will also potentially make a huge difference in the javascript ecosystem. If the AI can implement a bunch of the libraries you've been importing, your dependency tree gets less complex.
On one hand, this is terrible for a lot of open-source projects. Who's going to support all these little projects that see declining use?
On the other hand... business needs and models change. The need for people who can do visual and UX design, taking platform and actual use into account, and turning that into a good, maintainable implementation, won't go away. The CSS programming there isn't the hard part; the challenge is understanding the larger context and managing the project and delivering the technical parts of the project quickly, and adapting it quickly, are.
Can you provide a great open-source CSS library that you use in your projects, essentially as an advertisement for your design services, and insurance for if your design firm goes away? I would guess yes!
Can you provide paid access to templates that use your framework? I... I'm not so sure about that. Maybe a little? But I think that knowing what design choices you want to make for a particular project and having the judgment to find potential good fits and take feedback usefully and iterate are much more valuable skills.
It's a different business model. Maybe not a fun one to pursue. But you have to adapt.