For me, THESE are the good-old days.
In terms of recorded Mahler, I would agree with you totally. When I started collecting Mahler there were few options for symphony sets: Abravanel, Bernstein and a compilation of mosty awful recordings on Everest. Now we have glorious sets by Kubelik, Solti, Tennstedt, Bertini, Maazel, Bernstein (again and again), Chailly, Haitink, Abaddo, Thomas, Nott, and even Gergiev, Zinman, Kondrashin (most of it), Tabakov, and several others gave us fine recordings that are well worth hearing. I've always insisted that Mahler demands the latest, greatest state-of-the-art sound and most recordings done in the past 30 years give us more than adequate sound, something that Walter never had. If any Mahler symphony pushes the envelope of sound reproduction to the limits it's the 8th.
I would have to disagree a bit about the golden age of Mahler conducting. In the past there were some real personalities who seemed to draw something real special from those scores that eludes some younger conductors today. They knew that there was more to the music than being a "concerto for orchestra", which is how Mahler is far too often played. A certain conductor in LA epitomizes this. It's just one of the frustrating things about history that Mitropolous, Horenstein, and Scherchen never had digital sound. Or Stokowski's 8th. That could have been something incredible.