Three short lines, and they land like a quiet fact: the dead don't fall in love. On the surface it's almost obvious. Dead people can't feel anything, so of course they can't love. But the way the poem is put makes you stop and think about what that really says.
The key is the phrase "fall in love." Falling is sudden, risky, a little out of control. By saying the dead don't do it, the poem suggests that this kind of reckless feeling is a sign of being alive. Love is something you have to be alive to be foolish about. The speaker never says how they feel, but the flat, bare tone hints at something underneath: maybe a warning not to waste time, maybe a kind of grief, or maybe a tired sense of being emotionally numb.
The mood is hushed and stark. With so few words, the silence around them does a lot of the work, leaving you to decide which way to read it.