You're just not describing what you want properly. Looks fine to me. Clearly you have something else in mind, so I think you're just not describing well. My tip would be to use actuall illustration language. Do you want a wide angle shot? What should depth of field be? Oil painting print? Ink illustration? What kind of printing style? Do you want a photo of the book or a pre-print proof? What kind of color scheme?

A professional artist wouldn't know what you want.

You didn't even specify an art style. 1970s sci-fi novel cover isn't a style. You'll find vastly different art styles from the 70s. If you're disappointed, it's because you're doing a shitty job describing what's in your head. If your prompt isn't at least a paragraph, you're going to just get random generic results.