Why is that too high of a bar to clear? I’m not saying every game should be open source from day one (and tbh I think the people who say all software should be free have their head up their ass. People worked on it, some people want to get paid for that work).
However, how does it hurt Ubisoft to wait 5 or so years after shutting down the crew, then releasing the source code? By then, anything relevant to a competitor looking to ape off them, or a bad actor looking to cheat or carry out an attack would be irrelevant, and it would at least give the community a chance at creating something from the leftovers (even a dummy server that doesn’t allow multiplayer, but just lets the game pass any “can I connect to the master server” checks, kind of like what the Single Player Tarkov mod does).
I mean, Doom is the prime example. Would people care anywhere near as much about Doom if it never went open source? It would be a great game, but it would probably no longer be relevant. I can’t see that as being a bad thing for most companies (although I’m perfectly aware that the suits of major game studios will never see it that way).