There was plenty to like in those last Armstrong amplifiers and tuners, but the company's name had been on the wane for some time before them and they came out just as the audio world was starting to go silly. So they never succeeded in the market to the extent they deserved.
Some vintage equipment wasn't so good, but some was genuinely excellent and trying some shows that there may have been lots of technology changes, but there has been relatively little progress in the prime purpose, of reproducing sound.
To put this in perspective ask yourself how much progress human hearing has made in the same period
The people back in the fifties and sixties weren't stupid and they knew what violins, voices and electric guitars sounded like. They could sort the good stuff from the crap.
Loudspeakers are where some useful progress has been made.
David