The antonyms for the phrase "become adept in" include becoming incompetent, unskilled, inexperienced, clumsy, inept, unaccomplished, and novitiate. These antonyms suggest an absence of proficiency and expertise in a particular field, skill, or discipline. Becoming adept in something requires time, practice, and dedication, whereas the opposites of this phrase imply a lack of effort or ability to acquire knowledge and expertise. It is essential to note that being unskilled or inexperienced does not equate to a lack of potential or talent but instead implies that there is room for growth and development.