It is not black and white, though (excuse the pun).
Imagine for example a piece of software with a settings menu which maybe gets used once per user, if ever, and it is only for technical stuff (think: assign more RAM and change V-Sync method). For that use case, a simple, subtle icon which is perfectly findable for the target group in the rare case it is needed is perfect. A colorful, detailed icon might disproportionally distract and thus diminish user experience.
Point is - use the right tool for the right job, and thanks to the author for providing a specific tool!
Imagine for example a piece of software with a settings menu which maybe gets used once per user, if ever, and it is only for technical stuff (think: assign more RAM and change V-Sync method). For that use case, a simple, subtle icon which is perfectly findable for the target group in the rare case it is needed is perfect. A colorful, detailed icon might disproportionally distract and thus diminish user experience.
Point is - use the right tool for the right job, and thanks to the author for providing a specific tool!