I remember, when I was 16, having a conversation with a fellow student about Robert Heinlein. This kid's position was that Heinlein was a "hack". He seemed to think it was obvious.
The opposite was obvious to me. He was a "genre writer" of course, but that doesn't make one a "hack". A hack, as I understood it, is someone who just churns out work for money, without believing in the value of his own work.
In principle, a mainstream "literary fiction" writer can be a hack.
But Heinlein sure seemed sincere to me, and he tossed off suspenseful stories full of his own distinctive world view.
Think outside the box.