The phrase "take off as" generally means to gain popularity, success or momentum in a particular field. Its antonyms can include phrases like "fail to catch on", "fall short", "falter", or "wither away". These indicate instances where something hasn't been able to attain its desired goals or gain acceptance. Other antonyms of "take off as" may include phrases like "lose momentum", "die down", "decline" or "dwindle", implying a loss of popularity or success. It is important to note that these antonyms do not necessarily signify failure, but rather a lack of growth, energy or progress.