Apologies for the late response but this comment demands it:
CJS510 wrote:
As an It professional I can say on thing if was that harmful apple wouldn't let you buy it from the Apple Store.
That is basically true, but MAS software can absolutely be detrimental to a Mac's operation without being harmful.
Case in point: a colleague brought a Mac to me that didn't seem as responsive as it should have been. Upon questioning her she admitted using CMM to "clean" it, but all remnants of the program had been removed. Yet it still performed poorly. Booted Safe Mode, no help. Still not running well. Fan blowing, etc. I could find no obvious culprit. Using Console (which I do not generally recommend) the problem turned out to be a macOS process that was encountering constant I/O errors writing to a file. It turned out to be a log file that CMM "cleaned". File no longer existed.
What could go wrong with deleting a simple log file? Apparently, a lot.
Log files are created and maintained by the system. macOS expects them to be present. Perhaps Apple's engineers should have foreseen the possibility of users sticking their fingers where they shouldn't be stuck, and anticipated the need to create a required file that mysteriously vanished. But at some point it's unreasonable to anticipate every possible dumb thing some malicious or merely inept developer might do. This program met all of Apple's App Store requirements. It was not "harmful" yet it still caused a perfectly good Mac to perform poorly.
This is also the reason I advocate erasing any Mac that has ever had any such "cleaning" product installed. It saves time. Instructing someone in Console over a support site like this would be an exercise in futility.
For the Mac in question, I created an empty log file where it should be and all was well.
The issue here is that most of this stuff that's done by the software you can do your self, if you have knowledge or knowledge where to look.
If you have the knowledge of where to look, then you would have the knowledge to not use such things.
CMM sycophants typically defend its use by saying "it's perfectly ok to use" followed by the slightly haughty disclaimer "... if you know what you're doing."
- If you know what you're doing, you don't need it.
- If you don't know what you're doing, don't do it.