The point is there must be some force of opposition to the MC. That force is not necessarily a person.
It can even be an internal force, not an external force. I'm thinking of the movie Once, where the male MC's main conflict was with his own insecurity about his worth as a musician. The female MC's role was to get him out of that mindset and send him on his way. That was one of the few movies where I really wanted to see what happened to him/them. I wished there was a sequel (Twice? Once Again?) that showed more of the journey for both the MCs.
I want to know what happened to her. There was clearly a story there with her situation and what she may be dealing with. Like... the events that lead up to her showing up in the vacuum shop. Call it "Once Before"
That is why I said an opposing force, and didn't specify beyond that. Fight club was also an internal conflict, but well hidden through the story.
