How do writers think of plots?

A genuine question. I've been thinking of starting to write books or at least one book, but I can't think of what to write about. I feel like, whatever I can think of has already been written in a way, especially if I want to write something dystopian. And if I think of something, I can't seem to move forward from that. I can't seem to be able to create the fictional world around that idea.

So even if I can think of an idea to write about, I can't create a whole plot around it. I get stuck not far from the beginning and start feeling like my ideas suck, but I think I just might be doing it wrong.

Can anyone share their techniques how you as a writer do that? How do you make an idea into a whole interesting book, that actually makes sense and where everything that happens comes together in the end without leaving any plot holes? How do you plan it, so that halfway you don't feel like deleting everything because of a plot hole you can't easily fix?