Fortunately you can copy the binary from an older version of Windows.

At least you could thank Microsoft for being backwards-compatible.

I've done this with calc.exe since ~Vista.

the Notepad team

That's probably part of the problem --- Notepad is something that could be written by a single person in less than a day (it's not more than a wrapper around a Win32 multiline editbox.) Yet give a whole team of multiple people the task of "modernising" it, and work will magically appear to fill the available resources.