FWIW, the AppStore also sells some apps (anti-virus, so-called cleaners, etc) that can be detrimental to your Mac. That's because the App Store accepts any apps that conform to their developer guidelines and they don't test them for efficacy. Just search "anti-virus" in the AppStore and you'll find tons of worthless junk.
On the other hand, some apps that actually perform well aren't accepted. A case in point is Malwarebytes. Malwarebytes was developed by one of our own colleagues here in ASC and is about the most proven anti-malware software for Mac. It is used and recommended by Apple techs themselves. But it doesn’t conform to AppStore guidelines because in order to do its job it needs to search parts of the system the guidelines prohibit.