Is it possible to change default icons in macOS High Sierra?

Question

macOS

Good day!
As a person who recently moved to MacOS, I am interested in a number of issues, one of which is the ability to replace the standard system application icon (in my case, "Notes"). The classic drag and drop of the ICNS file on the icon in the "Properties" window does not help. With other applications I have installed, this goes away, for example, the icon in Word changes. But it is the system applications - alas and ah. At the same time, as an administrator, I do not have full access to the standard application. Accordingly, I concluded that replacing the icon is impossible due to the lack of the required access level (pressing the lock icon, of course, does nothing - I can’t change the access level, only the system has “read and write”). And I don’t want to farm anything,
Asking those who know to answer whether I'm right or is there some way to still change the system icons? Just to close this topic for myself and not look for a wasted method that does not exist))
PS: I've always been annoyed by slanted icons in MacOS, both when using Windows and now. Therefore, I am looking for ways to ennoble the appearance for myself personally, as they say, in taste and color :)

Answer 1

Everything is changing perfectly, when replacing the icon on the application from the App Store and System, the root password is requested and that's it.