All the above I agree with. But I am struck by the assumption implicate in the question, that newer recordings should sound better than older ones. In many fields, newer is almost always NOT as good as older. In Vintage Drums for instance, the most desirable and expensive snare drums are Ludwigs from the 1920’s. Not just because of their rarity and collectability, but because they sound better than newer ones. They were made in a way (I won’t go into the details here) that was expensive (they were over $100 in the late ’20’s, a LOT of money at the time), and the Great Depression brought an end to their production. No one has ever resumed making them the way they were in the ’20’s, certainly not Ludwig.
Microphones and other recording gear from the 1950’s and ’60’s is very desirable amongst recording engineers, and fetch high prices when sold. They often possess a sound quality rarely matched by newer gear, just as some (Many? Most?!) old recordings sound better than newer ones. Age or era alone is not the determiner of quality. I don’t understand the assumption that it is, could, or should be. A 1950’s and ’60’s Corvette was a far better car than the Corvette of the late 1970’s and ’80’s, when emission regulations forced a change in engine and exhaust design.
Contemporary recording equipment and technique is not necessarily about achieving sound QUALITY ya know. Not to mention the fact that recording engineers these days are too commonly somewhat ignorant practitioners in their field. I was at a session where a "school" educated young engineer placed an ambience mic right in the upper corner of the studio and recorded the sound emanating from it. The very spot we audiophiles put absorption because of the nasty sound that room corners produce! His "education" obviously did not include even basic acoustic theory or he would have known what that would sound like when recorded. Recording engineers of the ’50’s and ’60’s had learned their craft the old way---not in a "school", sitting in a class, but working as an apprentice, a "second" engineer, side-by-side with a master. They were in many cases radio engineers in World War II, and when they returned to civilian life went to work in early recording studios, before there was even such a thing as a tape recorder. By the time they were making those legendary great sounding 1950’s and ’60’s recordings, they were masters themselves. There is a fantastic documentary entitled "Tom Dowd and the Language of Music", in which Tom, engineer of many great recordings (as you will learn in the doc), tells us all about it. A MUST see, it’s available on DVD.