So I went out to take a look at some magazines both digital and print. It was immediately apparent why they are dying, and it's not just because people read everything on the web for free these days.
Every magazine I checked out was MOSTLY ads. Even during the Super Bowl, the commercials will be less than 1/3 of the total broadcast time. In the magazines the ads took up well over half of the available pages. Who in their right mind would pay money for that?
Magazines back in the day where nothing less than lavish. Elaborate foldouts of maps and photos in NatGeo. In depth strategy guides and customized demo discs on a monthly basis in video game magazines. All that is gone. The modern day magazine is a stack of ads with a few blog posts scattered throughout.
I'm going to guess it's some sort of death spiral. They lose money to the web, so they had less to invest in content and had to take more ads. That resulted in further loss of readership, and so on.
I do believe that a highly targeted and extremely high quality magazine can succeed in the present day. Of course the definition of success won't mean selling millions of copies on newsstands everywhere. It will mean having a loyal subscriber base that provides a largely flat, but sustainable, flow of revenue.