Some of the "advice" in CSSLint _warnings_ isn't just about performance and smaller CSS files, it's about writing maintainable CSS and being able to produce reusable classes or components for the development team. Depending on the project, that may or may not be a concern.

Irrespective of opinions on CSSLint, I'm not a fan of this kind of blog post. Doesn't do anything constructive. I didn't see any evidence of an attempt to engage with Nicole and Nicholas or raise concerns at the GitHub repo. That's a shame.