File Manager, or winfile.exe, was the predecessor to Explorer's file management aspects. You can use it on Windows 10 and 11 (and all the others) if you want to.
Program Manager, or progman.exe, was the predecessor shell to Explorer. It was included with Windows through Windows XP SP1 before finally being stubbed in SP2 and removed altogether in Vista. You can probably grab the binary from XP SP1 and run it in newer Windows versions, though.
The Aero Basic theme is particularly horrible though, I do wonder if that particularly unpleasant shade of cyan for the borders was picked to punish those who didn't activate Windows, or were to poor to afford Home Premium.
In the end it's one of those weird forgotten things, like the Windows 3.x colour picker dialogue that still lurks in a few places like Wordpad (although MS are "solving" that).
I think it's probably an artifact of drawing the window in a particular way using the Win32 API.
For example, you can also see the "Aero Basic" style if you do a Control.DrawToBitmap on a Form control. (According to the winforms source, `DrawToBitmap` just sends a WM_PRINT message.)
I am actually mildly surprised it didn't change in Windows 10, but maybe that part of the codebase never got updated. Who knows :)
(Side note: there's also this article[1] from 2004 that describes creating your own custom "designer" type application. It's pretty old, but it might be interesting nontheless.)
[1]: https://learn.microsoft.com/en-us/archive/msdn-magazine/2004...
On Windows 200 and XP you could install additional recovery console - which in later version has become a default addition to the system