I don't know any other
I disagree with this approach, and vendors that lock such changes down. If a user wants to replace every single app icon with a PNG or SVG of their choosing, that should be permissible at the OS-level. Users should always have the final say over their interface choices, and corporate or software-maker changes regarding aesthetics/interfaces should never override what the user has chosen for themselves.
Right now there's strong overlap in interfaces and experiences that make this difficult, if not impossible to execute on. Separating the two again is critical for computing to be accessible to all, as is maintaining a consistent experience throughout interface changes.
They are. You can replace the icon of any app straight in Finder, in the Get Info window. Copy the icon from somewhere else, click the icon in Get Into to select it, and Cmd+V to paste.
I mean, you'll need to get the original icon, but that's not too much work. I don't think Apple themselves should be shipping every high-resolution icon they've ever used for every app. OS's are already large enough.
The problem is that Apple has lost good taste and judgement. And their App Store obsession turned "we've made it so simple you don't need to customize it" into "you're not allowed to touch our precious OS, you additional-service-revenue-dodging bastards".
Every single one of these icons should be available to choose by the user.
Some folks make good icons; others do not. Taste is highly subjective, and this applies to user interfaces moreso than user experience.
Interfaces should always be customizable; experiences should always be consistent.