There should be one directory where all apps keep caches in subdirectories, managed by the operating system, evicting cached files as necessary using some LRU p

There should be one directory where all apps keep caches in subdirectories, managed by the operating system, evicting cached files as necessary using some LRU policy. (MacOS has well-defined cache directories, but nothing managing them.) Likewise for system RAM. Lots of apps are using RAM to cache with no way to coordinate.