I've interpreted "amateurs" as people that are not good at what they do. People that have a job or a main activity but don't try enough and don't have the minds

I've interpreted "amateurs" as people that are not good at what they do. People that have a job or a main activity but don't try enough and don't have the mindset to give the best of them. The whole list made sense from that point of view and less from "amateur" as a person that has a hobby.