Good question.
Music. In the case of Rock music, it was new and fresh in the fifties, sixties and seventies. It was also closer to it's blues roots, which made it more genuine. It is very difficult to create a song today that is not a rehash of some other song.
Naivete. Real naivete, not just letting the guitars feedback at the end of a song. Music used to mean more, so there was a greater range of acceptable emotions expressed. There were diverse individuals from Richie Havens to Ravi Shankar making music that was felt by millions. Today, so many musicians rely on image (or a lack of image, image) that it is very challanging to be naive about anything. Everyone is jaded and that makes the music stilted.
Church. Many of the greatest singers in pop history went from the altar to the stage. The depth of emotion that can be expressed when you either believe in something, or have felt that belief in church, cannot be created otherwise.
Meaning. I grew up in the Vietnam era and I think music meant something more then. Lots of us were getting killed. In this regard, unfortunately, we may soon be experiencing more meaning in our pop music.
Experience. Engineers and producers used to work under the supervision of an experienced mentor. After the Tonmeister programs, and apprentice programs of private studios, recording schools went on to train a few great engineer/producers. Artists were brought to professionals by PR experts who put them together with a writer, producer and studio like a great casting director teams up actors today. Today, anyone can walk into a Guitar Center with a decent credit card and come away with a 24bit 24 track recorder/mixer/sequencer/sampler/mastering suite/cd recorder. Giving a 10 year old a loaded pistol is not a good idea either.
Technology. Classical engineers were the first to adopt digital recording. In my opinion this was not due to the improved signal to noise, but to the incredibly improved WOW and FLUTTER performance of digital. If you have ever tried to record a concert piano on a 15ips 1/4" master, or worse yet tried to make a reference cassette for a client, you know what I mean. The rock solid stability of a digital medium was a breath of fresh air. However, there have definetely been ups and downs in equipment quality. Professional equipment has always swung 28 volts in my opinion. Now, we have "professional, -10db" systems that can't swing half that. Class A circuit design, discreet components, tube microphones; these will always have a special sound. I also agree that for some reason that I cannot understand, producers, or label execs are demanding their product be compressed to the point where they actually sound WORSE through a broadcast chain. Can't they be educated?
Sequencers. One time through a sequence and stick a fork in me, I'm done. These horrible devices are responsible for more unadulterated crap than anything else in the industry. Throw them OUT!
Digital editing/pitch correction. I have been guilty of moving a couple of bass drums in my time, however quantizing every beat takes the life (live) out of music. Keep the people in the music.
Best Regards,
Bill