The antonyms of "more full-fledged" are "less developed," "incomplete," and "immature." "Less developed" implies that something has not yet achieved full maturity or potential, while "incomplete" refers to something missing essential parts or lacking necessary refinement. "Immature" implies an inadequate level of mental, emotional or physical development. These antonyms can be applied to situations or objects that are not fully formed or realized, such as projects, ideas, or even people. By understanding and using the antonyms of "more full-fledged," one can better describe the current state of something or someone and acknowledge that growth and development are necessary for success.