I wonder why so many have the same issue then? I've tried a scan and repair in the past as well as a clean install... Doing it again rn just to be sure.
I'm definitely not player support and Modern Warfare definitely isn't a game I'm associated with but have you tried generating a new player folder? I had to do this a few months ago when something was being weird in June. You can see my zipped version here: https://i.imgur.com/ifxeeXz.png
Basically zip the "players" folder in Documents\Call of Duty Modern Warfare, delete your non-zipped folder (keep your zipped archive!), and then run the game.
If you keep that Modern Warfare folder opened you'll see the game launches...
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