Ive had this conversation with people before, it usually boils down to... people who say that something is too "childish or immature" for someone was usually told by their parents as a child that they have to "grow up" or to take more responsibility when they were young and they project these insecurities onto to others as a result

i usually just tell them to go bother someone else with their childhood drama because me and my yugioh cards dont have time for it