Theme. I think the theme of this story was supposed to be “make the most of what you have” or “live the life you have now.” Both of which I fully agree with. The android bartender told the hero that before he woke the girl up.
The fact that he woke the girl – a complete stranger he’d only seen and read about – is disturbing.
The fact that he didn’t have a solid reason for going on this voyage in the first place, and seemed to deflect when asked, is also disturbing.
Being the only person awake on a spaceship not due to dock in 90 years could lead to some interesting things. Such as, if it had been shot from the girl’s POV (she’d need some character development), we could follow her terrifying path from oblivious and trusting to knowledgeable and desperate.
For example, say he wakes her up and he’s a psycho who thinks he’s in love with her. She spends the rest of the story trying to convince him that she’s not the love of his life. When the crew member wakes up, she feels like she’s been saved. Then the guy – in a jealous rage – kills the crew member. When he makes the heroic self-sacrifice of being burned alive to save the ship – thus proving his worthiness of her love, she could be free. Maybe she’d trick him into going out to “save the ship.”
And the follow-up to that, maybe she gets lonely in another year or five, so she wakes some poor dude up. So – a study of what people would do when they’re lonely.
I think this could have been an original intent of this movie, but the story never examined loneliness. It illustrated it, but it didn’t discuss it.

Or maybe the ship, which should have fail-safes, doesn’t. (It didn’t seem to anyway). It knows they are awake, so it tries numerous ways to put them back to sleep. The bartender could turn from a good guy to a bad guy easily.

Or the crew member could be a psycho and try to either put them to sleep, kill them, or detain them in some manner.

Or they could valiantly try to save the ship, and make one last call for help – which would be played as an over-dub over their disintegrating particles. Instructive tragedy for future spaceship manufacturers. Or they could have to blow up the ship to save themselves from it – because it started to wake up other people and then hunt them down. Kinda like a bored cat playing with a mouse.

For an actual romance, there would have to be, well, romance. Maybe the actors didn’t have any chemistry – so their “romantic” interludes weren’t.
If I were to make this a romance, I’d have the girl be a crew member. I’d get to the ship’s imminent destruction much sooner. It’d be like Groundhog Day and Cast Away mixed.
So hero wouldn’t earn the girl until he “lives the life he has now” and learns new skills in order to fix the ship.
The girl would be resistant and uninterested until the ship started to self-destruct. She’d be anti-whatever the hero is. Then she’d have to work with him. And once the ship was saved, she’d hook up with him.

And enough about Passengers. Visually, it was neat. Story-wise, not so hot.