To begin with, his potential audience is minuscule. Then, too, the chances of having his works performed are severely limited.
Record sales are most unlikely and public recognition and acclaim are all but out if the question.
My intuition suggests that you, possibly more than other people, have wrestled with the question I am about to ask. The answer, obviously, is that you love it, but as a composer among composers I feel myself to be a shrub in a forest of trees. My voice is lost and will stay lost except for an accident of fate. I have dealt with the problem essentially by ignoring it. That doesn't mean he has to decide if he's good, but, rather, if he's that funny and rare kind of bird who has to sit on branches and sing.