I'm using System76's Pop_OS icon theme in Gnome Shell, and like the clean look of it. It changes the icons for a good number of popular applications too, which results in everything looking neat and coherent.

> Good. My computer is not your billboard.

Yes, seriously. If a user runs a free software desktop, chances are the ability to change things according to their wishes is part of why they use it.

> Changing third-party apps without any QA is reckless, and would be unacceptable on any other platform.

Which is why I use a platform that does grant me that freedom as a user.