The problem for music mags, too, is the biting-the-hand-that-feeds-you problem faced in much entertainment journalism. Upset a source and its very easy to withhold access.
Time, too, is a big issue. The best Rolling Stone pieces from yesteryear came from lengthy time spent with subjects. In my feature writing experience (mostly for city monthlies), the best, most telling material came from spending time with subjects, not from half-hour phone interviews supervised by publicists. But the latter is increasingly common as artists make greater effort to control information about them.
So is there still a place for music magazines? In his essay, Weiner asks: "...should we mourn dead music magazines or simply shrug as we pass the funeral?" I ask you the same question.