I think reaching back to Somnium and The New Atlantis as examples of early science fiction is kind of like pointing at Bosch as an early example of Surrealism - yeah, it fits the definition but it exists in a bubble, divorced from the rest of the movement without influence for or by the rest of the body of work.

Can't remember who it was, but someone (Bruce Stirling?) pointed out that the important fact to consider about Cyberpunk in general and William Gibson in particular was that it was the first science fiction since WWII that didn't take place in either the incredibly distant future or after a nuclear apocalypse had wiped out everything else. In other words, Neuromancer was the first book to imagine a future with Russians that were not radioactive. seen through that lens, dystopian works are almost heartening in that they don't predict the wholesale slaughter of humanity in order to set the tableau.

And hey - they're generally only dystopian for the protagonists. Most dystopias have some sort of ruling class that oppresses Our Heroes for whom shit is actually pretty sparkly. My favorite Hanna Barbera conspiracy theory is that the Flintstones are the Morlocks of the future, toiling on the ground and living like cavemen to provide for the Eloi in the clouds, the Jetsons...