What is the term for a person thinks that there might be a god but that it is not worth worshipping?

Unbeliever.

He might be an unbeliever because he has not heard enough to believe, and that is corrected by hearing the gospel. He might have heard enough to believe but he rejects it. The correction for that is to change his mind, and that is what "repent" means: "think again".

Nowadays a lot of people think they can make up their own religion, any way they want it. That is silly, but in fact there is a church based on that idea: Unitarian-Universalist.