It might have changed in recent versions of the app, but in the past I've seen in on a couple of computer and seemed a bit of bloatware.
There is not much (yet) that much harmful on Mac to suggest that you have to install defenders or other software that scans the computer in the background.
If you are using Clean my Mac to save disc space, one very good option is OmniDisk sweeper, that will give you a breakdown of what is on your hard drive. You can easily locate and remove (if needed) larger files. You need to have a basic understanding of what you are looking at.
Without downloading and installing any questionable software, your Mac will be fairly ok most of its time.
I've had to remote manage both my parents' MacBooks over the last few years and we never had any major issues. They also do not download and install any extraneous software - so that generally helped.
Most Mac apps are now notarised, can only be obtained via the App store (that is both a curse and a blessing) so that alone sort of makes it a bit "safer", even though, I admit I've seen some very sub-par software being peddled through the App store over time.
I would say that clean my mac is one of various software utilities that popped up in the Mac space after the big "switch" campaign ages ago.
Suddenly a lot of windows users jumped on the MacOs platform and some software houses were quick to make some profit creating these sort of apps that were a bit more of a standard in the Windows world.