The phrase "wert up about" implies excitement, enthusiasm or energy. Its antonyms would therefore be words that suggest a lack or absence of these qualities. Some possible antonyms for "wert up about" could include phrases like "disinterested," "unenthused," "unmotivated," "apathetic," "unexcited" or "uninspired." These words all suggest a lower level of energy, enthusiasm, or interest, which is very different from the idea of being "up" or enthusiastic about something. While it's certainly possible to feel indifferent or uninterested in something, this is very different from actively feeling excited, energized, and engaged in a particular activity, event, or idea.