Valve plans to deploy a substantial improvement to how the Steam Deck handles its shader cache files, which should help with storage concerns.

Modern Warfare Remastered shader cache issue: Possible fix Shader cache issues in Call of Duty Modern Warfare Remastered can lead to graphical glitches and frequent game crashes.

Delete the game’s shader cache. Steam has a handy way of deleting the shader cache, meaning the next time you boot up the game, it will restart the process of building the shaders.