The problem isn't that all games need multiplayer mode to survive, it's that publishers think all games need multiplayer mode to survive.
I have zero interest in multiplayer aspects, no matter what the game is, but I concede there are times when adding it has been done well (Assassin's Creed looks kind of cool; shame the single player turned to utter dog shite).
Then you have games like Dead Space 3, which people tried to defend as 'not forcing the multiplayer on you' but that doesn't excuse the fact that a huge chunk of the game's campaign is withheld from you unless you're willing to go online and partner up with someone.
If you refuse to do that, as well as losing out on gameplay content, it also completely fucks up the story because the motivations of your little buddy make absolutely no sense when he goes from 'GTFO Isaac' at the beginning of the game to 'BFF Isaac' at the end.
What I'm getting at is that a robust single player can still carry a game --the first two Batmans made that abundantly clear-- but publishers and devs tacking on a consolatory, shallow multiplayer will almost always result in disaster because it alienates the original fans and disappoints newcomers who can get the experience they want, better, elsewhere.