The CSS Zen Garden worked because everyone was using a single markup file. In real life, it doesn't really work.

Instead of thinking of separation of concerns as a religious principle, think about what benefits it actually yields in the case of HTML.

When the markup is completely separated from its styling, this means that the CSS rules need a way to be mapped onto the DOM. This involves specific elements, organized a specific way. If anything is out of place in the markup, the properties may not apply as intended. Similarly, if the CSS doesn't account for DOM structures, then you need modify rules or add new ones.

This way of mapping is an implicit structure. It's something extra that's required, beyond the source code that's there. It can be computed by the browser, but it's not explicitly stated for a developer looking at the code to understand.

Contrast this with Tailwind, Tachyons, etc., where nearly all the structure is explicit, less complex, discoverable, and out in the open.

Hidden structure looks nice to the developer. The code "looks" clean. But understanding a code base's implicit structure is ephemeral, and there's inherent technical debt that will need to be repaid later.

Tailwind looks ugly, but there are no hidden abstractions or structures in the code, beyond its easy conventions and a minimal config file.

And, yes, there are ways to make high-abstraction CSS work, say, with a component library of known DOM patterns. But at that point, why not build the styles into the components directly, a la Tailwind, instead of adding complexity?

> The CSS Zen Garden worked because everyone was using a single markup file. In real life, it doesn't really work

The dream of the CSS Zen Garden never really extended beyond itself. That wasn't the point. The point was to show people "look at all these pages that look nothing like each other: they're all the same HTML." That was the magic.

Keep in mind the context: you still largely needed structural HTML to effect the layout of your page. Almost everybody was building with HTML where the markup was critical to the appearance. Frontpage, Dreamweaver, and every other tool generated almost no CSS—or at least no good CSS.

This isn't my interpretation. From the site itself:

> There is a continuing need to show the power of CSS. The Zen Garden aims to excite, inspire, and encourage participation. ... CSS allows complete and total control over the style of a hypertext document. The only way this can be illustrated in a way that gets people excited is by demonstrating what it can truly be, once the reins are placed in the hands of those able to create beauty from structure.

The real divide isn’t separation of concerns or implicit vs explicit structure. It’s whether you have staff that wants to think about markup as a data format expressing domain entities and/or generalization of presentation concerns.

Most developers and organizations don’t want to and they don’t want to think why or what doing so would buy them. They will probably find the tailwind local maxima enabling that reasonably comfortable and may even repeat the familiar mantra as has been done here. It especially pairs well with unreflective product management, which is the most popular kind of product management.

> Tailwind looks ugly, but there are no hidden abstractions or structures in the code

Verily, Tailwind is the assembly language of CSS. No structure, no semantics, no abstractions, only twiddling specific bits of visual representation.

To turn to it is to admit that your product lacks the structure and the design vision that allow to use some abstraction ("semantic classes"), and that all you can usually do is to patch some areas of it, disconnected from the rest, and unable to touch the rest (lest it goes down in flames). Assembly is definitely suitable for patching.

This is often the endgame of old large products that changed hands and directions many times, without much care.

I also dont think you can cleanly separate HTML and style. Technically you can separate them but doing so in practice just handicaps your design and ability to express things in HTML and CSS (Zen Garden prohibiting css 3+ in most cases).

People have this idea that they should be decoupled. You can do that if you really contort them. Naturally, they are coupled.

The structure of HTML puts constraints on the style. You have to know about the style when writing HTML, even in this Zen Garden project. You can't escape the style and HTML understanding each other. If you have a compelling reason to make a broad range of styles swappable then OK - but you are constraining the design space considerably and there is usually no reason for this complexity and reduction in expressiveness.

The document and the style depend on eachother. You see this with localization. You might need to change spacing or padding or breakpoints to accomodate different languages (text being different length in different languages).

This is why all UI paradigms tightly couple style and structure. QT, GTK, SwiftUI, Flutter, etc. Its the same with CSS/HTML except for people who delude themselves into thinking these were supposed to be loosely coupled.