I wouldn’t use a complete macos theme with the logo and everything, but the mac design language does have some pretty nice details that even help usability.

For example, I love the double outline that macos windows have, the normal darker line and another lighter inside. To me, it really separates windows when I am working with several, and they overlap (I use mac at work), in addition to looking nice and giving some depth. That’s just a little detail, but there are many like that one that is easy to see why someone could appreciate them.

Obviously it varies from person to person, there’s also stuff that I don’t like, but I do can see why someone would use a theme like that.