BUT
I don't actually understand your sentences for the most part. I really had to work to glean what you were talking about.
I'm not trying to be insulting here; sometimes I write in inscrutable ways too. But - could you reword a few things so I know what you're trying to say?
The general point was that "Improvement" that ruin muscle memory usually aren't. It should be the most basic UI design principle.
One should be able to instinctively click on the Gmail icon while focused on the task at hand. If the icon isn't where one expects it to be you are no longer doing email things. Same goes for having the user search for the inbox inside the application. If they can't find it they are unproductive and feel dumb but they aren't to blame. Some bad designer came up with the brilliant idea to call it "all mail". The inbox is expected to live at the top of the menu. You can't improve it.
It's such basic stuff. It's like someone used your tools or your kitchen and put everything in a new spot. Eh, I mean the wrong spot.
I could give 1000 example inside windows but it seems everyone is trolling their users. They all want to create the new and improved slashdot, now without threaded discussions! - Hurray!
I'm not sure what this sentence means. Perhaps you already knew that Gimp's monochrome icons can be replaced by colorful ones by going to the Gimp settings under Theme -> Icon Theme, and unchecking the "Use symbolic icons if available" checkbox. That may be what you meant by "some place buried deep in the settings". But if you didn't, at least now you know how to get the colorful icons back.
The reason I'm making this comment, though, is to contrast it with Windows. A comment by chasil, left shortly after your own comment, said that "[a]n attentive steward of Windows would allow older gui themes (xp, Win7 Aero, etc.) to be applied for the nostalgic." Gimp has done just that: in Icon Theme, you can choose the "Default" or "Legacy" icon theme, so if you got used to the older icons, you can get them back. And you can still use the newer icon set if you like, but get the icons' colors back by unchecking a (confusingly-named, the name definitely needs improvement) checkbox. Windows doesn't have any built-in way to get the older themes back; if you want Windows 11, or even 10, to look like Windows 7 or XP or whatever version you trained your visual memory on for years, then it takes third-party software to make that possible. (And it may not even be possible, I haven't checked).
When even one of the most infamous-for-confusing-UI pieces of open-source software (I mean Gimp, of course) is doing a better job of providing good UI than Microsoft is, Microsoft has a problem.
It doesn't have to use different window layouts, just differently themed decorations. Changing the default wallpaper is a simple way to do it.