It started out with an interesting premise -- being able to spend your time in solitude with the person you love. It quickly fell apart. First of all, it was annoying AF to keep having all the flashblacks/scenes beating you over the head with just how cutesy and perfect this couple are for each other. The movie was probably stuffed with 50% filler of just the two of them laughing, laughing, laughing. Nobody laughs that much. Oh, and rolling around on the bed, again, laughing, playing rock/paper/scissors, and games. Which was weird, because this couple had zero sexual chemistry. Glad we were saved from any awkward sex scenes, since they acted more like brother/sister.
I could overlook a lot of that, but the story just went nowhere interesting. If they'd cut out half the cutesy crap and added in some scenes showing them breaking into their neighbor's house for supplies, or how they got food etc., for months, that would have at least added some interest.
It didn't help that there were huge plot holes that nobody even tried to address. Why were they so incurious? Didn't even bother turning on the TV, computer, or radio for news? But, didn't have newspaper delivery one day and that was all the proof they needed that all human life had disappeared?
It didn't even work as a comedy. I don't find it hilarious to watch tedious scenes showing how cute a couple is together and how much they laugh. Nothing funny happened. Nothing scary happened. It should have been a short film, because it ended up being a movie full of filler.