I get the sense most Neal Stephenson books don't actually end on either an optimistic or pessimistic note, they just...end. He doesn't seem very interested in passing judgment on whatever future he imagines, he just wants to imagine it. The world simply is the way it is, and humans will continue to be humans, and that occasionally involves doing shitty things. Technology just amplifies that.

He's pretty good at imagining it too - The Diamond Age was published in 1995, just as the Internet was beginning to take off, and yet it envisioned The Internet, videoconferencing, smart paper, drones, and a whole bunch of other technological innovations that didn't catch on for 15 years or so. Cryptonomicon was published 10 years before Bitcoin but fully described two of its biggest use-cases, remittances and digital gold. Snow Crash had the "America is good at only 4 things: music, movies, microcode, and high-speed pizza delivery" line in 1992, 20 years before it became true and right as the rest of the country was celebrating us becoming the sole superpower.