I don't know why Apple would classify this as "not useful". I've been using such a utility for years and find it very useful.
At any rate, I have always used "Keyboard Cleaner.app" (http://jan.prima.de/~jan/plok/archives/48-Keyboard-Cleaner.html).
I continue to use it because it blacks out the screen during cleaning, which makes it infinitely easier to see all the smudges and smears in order to get a very clean screen.
I'd love to switch to KeyboardCleanTool, since it's better maintained and also locks out the Touch Bar, which is very useful. However, without the screen blacking feature, I find myself always using Keyboard Cleaner.
Please consider adding an option to black out the screen? Thanks for listening!