It is both, and herein lies the problem with HTML and the quest for purity. The content you display in a card differs from the content you display in a different context.
The world is filled with "bad examples".
> so it deserves to be a class.
I guess I haven't looked at <article> docs since it was introduced many years ago [1]. Talk about "semantic" lol. The entire definition has been twisted and turned to be nearly indistinguishable from a <div> element. TIL that "product card" is an "article" [2].
I guess the reason why people use divs is that they may look for a corresponding semantic element, but don't see it in the list, and don't look into technical details, so reach for a generic div.
Interestingly enough, best practice is (or was a couple of years ago) to actually use a card as a list element in a list, see: https://wpaccessibility.day/2024/sessions/how-to-design-and-...
[1] Originally, of course, they were always meant for texts that "could be published or syndicated separately if needed" https://www.w3.org/WAI/GL/wiki/Using_HTML5_article_element
[2] https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/... while the spec still talks about mostly actual articles and text content: https://html.spec.whatwg.org/multipage/sections.html#the-art... HTML as text-only and text-centric markup is uniquely unsuited for... well, almost anything (even for most text use cases).