Some boys don't want marriage to bind them. On the one hand, they are not mature enough to undertake this responsibility. On the other hand, they feel that being single can be casual and they don't need to be responsible for anyone. No one can restrain him.
If you think he is your ideal candidate, you can give him some time. If this time is too long, you can explain it to him. If you think you can wait for him, be patient. However, you should be prepared: in case he waits for several years to find someone better than you, you will wait for nothing.
Love requires that two people like each other very much and have feelings (that is, calls), and the age gap cannot be too big. If the age gap is too big, there will be no language communication, and the consequences brought by the generation gap are serious. At that time, it will be too late to regret.