"Soylent Green is people!" is a punch line. Even Cloud Atlas cited it as a comic touch, even if it also used it for foreshadowing.
The movie is very much a love story with some problems in its female characters. Much worse, the hero doesn't exactly win his lady love. I think in the long run the romance audience will find those too aspects too off-putting. But the SF audience will find the romance too icky. In the end, the movie violates the maxim that you give the audience more of what it liked before.