The phrase "more crackerjack" refers to something that is exceptionally good or outstanding. Antonyms for this phrase could include "poor quality," "mediocre," or "subpar." These words denote something that is just average or even below average in terms of quality or performance. Other possible antonyms could be "inferior," "substandard," or "second-rate." These words suggest that the item or performance in question is not up to par and does not meet the expected standards. In contrast to "more crackerjack," antonyms like "insipid," "uninspiring," or "unremarkable" imply a lack of originality or excitement.