So I got an ultrawide, and to my disappointment, Call of Duty Modern Warfare sure didn't like it... I tried all sorts of FOV, Resolution combinations, and even looked up how to fix via Hex Edit, none of which was a solution for me. Then I stumbled on Widescreen Fixer r737 found here: https://github.com/dlrudie/WidescreenFixer/releases
In the settings(depends on your setup, I have 2 monitors 49" ultrawide (main) and 32" standard on top) you need to select Call of Duty: Modern Warfare, click on the gear and I am using v1.7.568 (multi-player) with a display count of 1 and uncorrected Resolution of 5120*1440 and also bezel corrected resolution the same.