CSS ICON is good for cases like, if you want to animate it, or style it on hover state in a particular way, of you need to prototype something fast on codepen where you don't want external assets files or long long pasted-in SVG code, this is much better.

The shortcoming is that you can't do any icon in the world with css. But if you already find this is equivalently appearance wise, the performance and code hygiene is much better than SVG or icon fonts.

also icon fonts are the worst way to do icon, here is the article about why: https://github.com/blog/2112-delivering-octicons-with-svg