That's an excellent question. As popular culture has fragmented into increasing numbers of subcultures, people who are into specific genres seem to have less time and patience for the bloviaters of yore. These types of magazines seem to be based on the old model.
Also, with message boards and online reviews, people can get an idea real quickly about where they want to explore.
Yes, as far as I'm concerned, the Down Beat, Metronome, Jazz Journal, Melody Maker and New Musical Express of my youth have been replaced by the online culture of this forum and blogs by people like Ted Gioia, Marc Myers and David Brent Johnson (ghost of miles).