I would say that Shelley does challenge the romantic view of the Prometheus myth.
In this myth, Prometheus is portrayed as the hero. He is someone who has taken fire from the gods and given it to human beings. He is punished by the gods for taking something they did not want humans to have, but he is a hero to human beings.
Shelley is much more skeptical of scientists who take what the gods have kept for themselves. She portrays Frankenstein as a man who has overreached because of his own arrogance. He is not a hero -- he gives nothing to humanity.
Shelley is saying that it is not admirable when people try to take things that are better left to "the gods."