It only ended with Count Zero if you’re looking for novels that were treated as significant by “mainstream” readers. To SF fans, the only people who actually read those magazines, there were a bunch of significant novels published in magazine in the late 80s and early 90s, and the a few more through the mid-2000s. I think that Michael Michael Swanwick’s Stations of the Tide is one of the best SF novels of the 90s, and it was serialized in Asimov’s. It was popular at the time, being nominated for a Hugo and a bunch of other awards and winning the Nebula. I don’t know if Swanwick ever got attention outside of SF circles, but he’s a big name in science fiction and fantasy. He had two stories adapted by the Netflix TV show Love, Death, & Robots (which I’ve never watched), so people might know him from that.

This isn’t really what we were talking about, but the month before the first Game of Thrones book came out the novella Blood of the Dragon, comprising the Daenerys Targaryen chapters from the novel (I’ve never read any of this stuff so that doesn’t mean anything to me), appeared in Asimov’s, with this sexy cover

As far as magazine nostalgia: alot of science fiction fans now are nostalgic for an era when the popularity of short fiction wasn’t so dependent on social media hype, which favors online publishing over print magazines. But people like the fact that so much of the short fiction now is being made available for free, and that there are more outlets for it than there were in the 90s, when 3 few editors published over 75% of what was easily available. I can’t appreciate all the online publishing because I can’t enjoy reading fiction off of a computer screen.