If you are talking about the BREACH vulerability, CSS won't reflect user input. The attacker is not able to observe thousands of slight variations of the same file, which is how this attack works (simplified). Transferring static files compressed over HTTPS is completely safe to my knowledge.

So maybe if you inline your CSS into the page this comes into play.

Also I never said minification is useless, only that you need to compare plain+gzip vs minifier1+gzip vs minifier2+gzip to see the _effective_ size reduction.