I think that's an unfair strawman, because they are saying that UI does matter, only that their opinion of "modern UIs" is that they are often worse, not better.

Someone mentioned an "in between" option and that's where I personally tend to land as well. A lot of modern websites are so media and JavaScript heavy that they take a long time to load, have many layout shifts and feel sluggish when you use and navigate them. That is not good user experience.

On the flip side, I think there is a lot to say for "responsiveness", font choices and media that helps the user experience. I am a minimalist, but legibility of copy and making intelligent layout decisions relative to the viewport size are "modern" techniques that can greatly aid UX when understood and applied properly.

UI matters, that's why we're praising it.

I don't know what you're talking about. That's a beautiful, clean, and clearly-organized site.

UI matters, and modern UIs are horrible