I wasn't surprised to see that sales of classics/reprints in science fiction haven't gone down but it's all new publishing that has.
Science Fiction is plagued with all the same problems facing comic books and tabletop gaming: the entire publishing industry only cares about representation and winning industry accolades for said representation and it isn't resonating with fans so sales are cratering. The industries are focused on people who aren't already customers and they aren't attracting them as customers either.
Disney keeps doing this absolutely baffling thing where they purchase male-dominated (by fandom) IPs and run them into the ground (Star Wars, Marvel, and I assume Epic Games' catalog soon-enough). They've acknowledged in previous years annual statements that their marketing primarily targets girls and that they have problems marketing to boys and men. These big IP buys were an attempt to diversify and all they've done is double down on their exisiting customer.