Martin B. Kantola said:
Exactly but totally impossible to achieve and not even desirable as been pointed out by greater men

You are so right that we should carefully ask ourselves what we want. In my microphones, I want to hear that engaging quality you speak so well about. It doesn't seem to be in conflict with any other property really, and it's not simply distortion or a peak in the frequency response either. Certainly not some magic sauce ;-)
That's a point that's often misunderstood by "the small diaphragm police". They often argue that a recording should be as clean and linear as possible, and if you really want some kind of flavor, you could add that later on. Like sauce on a schnitzel. However, there is simply no way to add some U47-flavor. Also, it isn't just a flavor, it is a perspective. A microphone represents a certain way of listening. A U47 has a kind of mojo that you can't just add after the fact. It inspires you (the performer) the very moment you use it. There is no retroactive inspiration plug-in.
Martin B. Kantola said:
Might say that I'm more interested in the impact of an experience than what the ear is hearing. For some reason (and the U47 is a good example) an engaging microphone can work for in surprisingly many applications besides vocals. While the people who designed the classic microphones were engineers, they certainly used their ears a lot. Because that's all they had for quite some time. The human hearing and the human voice is a reference that can probably not be ignored, it's built into all of us.
I'm sure they used their ears, but they also invented and developed measuring devices and methods (Neumann used to build frequency plotters ("Pegelschreiber") and measurement microphones back in the day). In that sense, little has changed in development. What has changed is the market. In the 50s and early 60s, there weren't many companies producing studio grade microphones. The market was small and most microphones were bought by broadcast firms. In Germany and many other European countries, radio and TV were state-operated only (In Germany that changed only in the 1980s).
In a way, money didn't matter as much as it does today. When you build a TV or radio station (and state-operated ones tend to be fairly big) and raise buildings, buy all inventory and have dozens or even hundreds of people on payroll, a set of microphones, even expensive ones, isn't that much compared to the total cost. And since there was very little competition, people had to buy the few mics that were available at the price they cost. There was no urgent need for manufacturers to meet certain price points. Technical brilliance was more important than saving a few bucks.
There simply was no alternative to a U47, when it came out. And even if there had been a cheaper alternative, a state-operated radio station would still have bought the more expensive mic, if it was technically better and/or more usable. When the U47 came out, it was a landmark. It was
much lower noise compared to anything that came before (and even a lot of mics 50 years later!). Plus you could switch between cardioid and omni, which was a brand new feature then. It also sounded more brilliant than any other mic available then.
Today mics have to make a certain price point in order to beat the competition. In order to survive, mic companies have to pay a lot of attention to the market and react to its needs. Average sells better than ultimate.