The speaker is in love and hiding it. The poem opens with the three words "I love you," set in quotation marks in the subtitle, and then the lines pile up: "I miss you," "I wish I could kiss you." Those first lines are honest and direct. Then comes the swerve. The speaker says they won't admit any of it, because they assume the other person doesn't feel the same way.
What makes the poem work is how the short, broken lines imitate someone losing their nerve. The rhyme of "you," "could," and "won't" keeps things light and quick, almost like a chant, until the speaker slams the door with "oh wow / emotions are / lame." That ending sounds casual, but it reads as a defense. Calling feelings lame is easier than admitting they hurt.
The mood is wistful and a little awkward, with a touch of self-mocking humor. The speaker has said "I love you" only to the reader, and perhaps only to themselves.