It is very much possible to mod unity games through the use of c# reflection. This, of course, is very hard, so libraries like harmony have been written, and ar

It is very much possible to mod unity games through the use of c# reflection. This, of course, is very hard, so libraries like harmony have been written, and are now packaged in launchers like Unity Mod Manager that you just point to a class to patch the loader in and off it goes. Also take a look a ilSpy for viewing decompiled c# from IL. Unreal games are a tad harder but loaders do exist, the main problem is that they are generally compiled to machine code instead of Il, so you need to generate the symbols for that version of unreal engine yourself and thats not really fun. Overall the recent trend of all games being either unity or unreal means that only 2 loaders need to be invented, and that's exactly what happened.