It means exactly that. I have lots of lady friends that I think are super attractive but I don’t want to be in a relationship with them. With each one, it’s a little different. Our ideas about life might be different, we might be too far apart to make a relationship work, we just might not be romantically compatible, even if I feel we’d be perfectly sexually compatible. We might not be romantically available at that point in time or waiting for someone to truly blow our socks off. I might feel that she’s just not good for me, not in the she’s-gonna-get-me-hooked-on-drugs sense, but rather in the fact that it might get me to continue relationship patterns that I want to leave behind.
There’s as many reasons as there are people. We can only ever be in a relationship with a small number of people in life compared with how many people are out there. So it makes sense to be choosy. You’ll understand too when you start having some success in your dating life.