Earlier quoted context omitted.
Yeah, when I read the article I thought "Great, more paternalistic advice that pretends we have infinite resources/time/money." Anyone who has ever done website or mobile development knows there is a huge array of browsers and platforms, and supporting the very long tail of configurations is sometimes nearly impossible, let alone almost never cost effective. When I last ran some web apps, we'd see substantial numbers…
Respectfully: To me these just sound like excuses. I can write a web page that works correctly on all browsers. We all can. That web page won't do much of anything, but it's possible. So, there is a baseline "target subset of HTML/CSS" that gives you 100% coverage. From there, it's purely developer choice: When you add something, are you choosing technology that is widely available and supported, or are you choosing…
Unless I am very specifically being paid for it, which I would love to be and I would enjoy doing because I love CSS, there are features that would rather make my experience, and the experience of the entire site better over the course of a decade+, such as nesting. Nesting has changed everything about CSS for me with project organization that makes changes significantly easier, AND significantly easier to pass off to another person. Now that it's at about 90% browser compatability[0] I actively use it in every single project I can, but it's still not supported if you haven't updated your browser in 3 years or use a random oneoff browser that may come with your knockoff smartphone.
It is an excuse, but it's also an honest question. Granted, not all projects are created equal, some of them are for people looking for bleeding edge technology, where it makes sense they would have their browsers updated. Some are government websites that should be accessible to 100% of everybody even if they're looking at your page on a 14 year old psp.