There are a number of people on this thread suggesting that the arguments in this article are fairly weak. That may be the case for some (or most) of them, but the accessibility concerns are right on point.

I work in digital accessibility and by using CSS background images as actual inline content, you're purposefully choosing a technique which does not have a well-understood accessible alternative. Which is fine, if you are one of the people who understand that alternatives do exist and how to use them. My experience suggests to me that the majority of web devs must not be in that category.

I thank the author of the article if including this concern helps just one developer or designer make more accessible images.