This is a fairly lofty and unrealistic goal. Unfortunately, the right for companies to keep their source code private isn’t going to go away anytime soon and if they were legally compelled to release binaries, the setup for a modern cloud based online experience is not for the faint of heart.
A more realistic goal would be to say that all products should be usable offline (with exceptions for impossibilities like an instant messenger or something)
If the online servers don’t exist anymore, there should be a path to functionality without them. For everything, given the rise of iot especially. If there’s a path to functionality without the online service there’s a path to preserving the game
Private servers are a thing for lots of big games. When the official servers shutdown or go bad, they tend to turn to emulation
Private servers don’t really happen much or at all anymore, “here’s a .exe you can run” idea doesn’t scale on modern online infrastructure well
Emulation is typically a very difficult thing to do, often requiring cracking the original game to get it to work with non official servers and also mapping and building out all the online subsystems. It’s rare.
