The architecture Lang's Metropolis was based on had already been imagined. And this has been true of most science fiction films ever since.
Regardless of how strong or weak the genre's storylines are, its sets are rarely less than memorable. When critics question a science fiction movie's credibility, it is often because design and visuals -- especially in the age of readily manipulated digital imagery -- appear much more important than the script or message.
Even when plots are thinner than celluloid film itself, it is still exciting to be transported through cities set far into the future, whether on Earth or light years away. Imagining remotely plausible buildings of the future is, however, hard to do.