If you message a guy and he gives you one-word responses to all your questions he’s not interested correct?

As a 79-year-old male with a lot of life experience, I would say he is either not interested, or is very shy and does not know how to carry on a successful conversation. Or Alternatively, he may not have a good self-image and feel if you got to know him, you would not like him. Some people are so shy they seem to go through life hoping to meet someone who will have a key or word(s) that will magically give them the ability to respond.