The binary for Microsoft Paint is called mspaint.exe, and there is no "paint" alias AFAICT -- typing "paint" in the run prompt results in "Windows cannot find 'paint'".

You could create a paint.bat file in C:\Windows\System32 (usually the first dir in %PATH%) that calls Paint.net instead. Something like this should work:

    "C:\Program Files\paint.net\paintdotnet.exe" %*

Add entry to. Works atleast in Win 11

   Computer\HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\App Paths