By that definition it would be hard to justify anything besides HTML, JS and CSS. That would also exclude TypeScript and every JS Framework there is on earth. That's hard to justify from every angle (development and business wise) imho.
That's not quite the definition they are positing. Many of the classes in Tailwind have near or actual 1:1 mappings to CSS, but with slightly different names or semantics. A better JS analogy might be something like Coffeescript; I remember avoiding it because it felt a bit superfluous and hence not worth the tax (of adding a tool).
With Tailwind, whatever the actual merits, the biggest points of traction (IMHO) are the frankly excellent example sites[1]. You can click through numerous examples, all load quickly and without ads, that give you numerous variations of components, layouts, and even full pages. You can spin up a vanilla HTML or React app and ship good looking pages very quickly, esp. if you are bad at design.
I use Tailwind for a SaaS app because of TailwindUI and I'm pretty happy with it. I also used the Marketing page examples to put together a website[1] pretty quickly.
When the app UI gets more complicated the need for design skills definitely creeps in. But, taking a step back, using a wireframing tool like Balsamiq, and having another look through the component catalog has gotten me pretty far. I'm happy with our ability to ship quickly.
Just an FYI, the logo on the site you posted gets deformed on mobile when there’s not enough space for it and the buttons on the right to live all on the same line.
