> As long as developers can opt into the new system (which they can with the manifest approach) [...] Microsoft has added a mishmash of flags in the app manifest

Could you please tell me, where are all these manifest flags documented? I asked about it a decade and a half ago at stackoverflow (https://stackoverflow.com/questions/5733085/application-mani...), and the only answer was "there isn't".

https://learn.microsoft.com/en-us/windows/win32/sbscs/applic... has the majority here.

I don't see why you'd need a separate flag for memory management, Windows version, printer driver isolation, awareness of long paths, and all of that jazz.

Still, https://learn.microsoft.com/en-us/windows/win32/sbscs/applic... has a setting to enable modern memory management.