The antonym of "more true-hearted" is "less genuine" or "insincere." The term "true-hearted" implies sincerity, honesty, and loyalty, all positive traits that enhance human relationships. Conversely, the opposite of these qualities shows that someone is less reliable, less trustworthy, and less respectful. While people can be less open and emotionally guarded for several reasons, a lack of genuine feelings can negatively impact relationships. It's important to reflect from time to time on one's attitudes and behaviors towards others to build strong emotional connections with friends, family, and acquaintances.