The phrase "gets off on" typically implies that someone receives a strong, perhaps even sexual, pleasure from a particular activity or sensation. Antonyms for this phrase might include dull, unstimulating, or unexciting. Alternatively, some might use phrases like "bored by" or "uninterested in" to describe someone who does not find pleasure in a particular activity. Ultimately, the choice of antonym will depend on the specific activity or sensation in question, as well as the context of the conversation or situation. However, by using clear and appropriate antonyms, one can often convey a completely opposite meaning to the phrase "gets off on.