When Apple identifies malware they can update macOS to block or remove it. This doesn't require the Mac app store to fix, and piracy doesn't have to be the cause, for instance Mac Defender was distributed through its own websites. Ironically it was suggested this fake anti-malware software could be avoided by using the Mac app store, but malicious anti-malware software has also been spread by and removed from the Mac app store. It's the same for users either way, Apple addresses the problem.

https://en.wikipedia.org/wiki/Mac_Defender

https://www.macstories.net/news/apple-promises-os-x-update-t...