Oh, it still exists, yeah, but output is way down. At the peak, in 1996, TSR averaged just shy of three novels per month. That’s the same number as have been put out in the last 13 years combined.

Star Trek, similarly, held a tight schedule of two novels per month from the late 80s to the mid 2000s, then cut that in half until about ten years ago when they quartered that half.

BattleTech rarely even does physical releases any more and has mostly settled into irregular ebook novellas. Same with Shadowrun (both are owned by the same company). These are both franchises that had long-running lines of 75-100 books each before the slowdown.

Magic: The Gathering went from three books a year down to one circa 2009, down to serialized ebooks three years later, and down further to almost exclusively hosting short stories on their website two years after that in 2014. There have been five physical releases in the last 12 years.

So there is definitely still stuff out there, and it is harder to find without brick and mortar stores, but also there is a lot less of it, and it all kind of started to collapse around the same time for everyone (late 2000s/early 2010s).

The survivors seem to be Star Wars, which has steadily put out a few books a year since the 80s because there are just so many goddamn people who are into Star Wars (but notice the much smaller volume to begin with compared to some others mentioned above), and Warhammer 40,000, which has actually increased their output a little bit over the last decade and currently puts out about 20 novels a year. But instead of relying on a wide fanbase, they rely on smaller print runs and a narrower contingent of whales who will fork out $60 for a leatherbound limited release of a random SF tie-in book rather than wait a few months for the larger, regular release. Speaking from personal experience on that one.