The term "more in-thing" could refer to something that is currently popular or trendy. Its antonyms would, therefore, include words that describe things that are unfashionable, out-of-date or unpopular. These words could include "unpopular," "outdated," "old-fashioned," "yesterday's trend," or "farcical." While it is natural for people to follow trends and adopt new styles, it is also important to recognize that these trends come and go. Therefore, it is essential to focus on expressing one's individuality and personal style rather than blindly following every new trend to avoid feeling left out or irrelevant.