Musicians in America enjoyed the "fat of the land" from the middle of the 20th century to the beginning of the 21st, but before that orchestral musicians who lived outside of major cultural cities (like New York, Boston, Chicago, and Los Angeles) had a very difficult time making enough of a living to support a family from music. Musicians had to work constantly (often playing commercial music) in order to make ends meet, and many orchestral musicians in smaller cities had to take summer jobs outside of music to make it through the "off season," but at least there was work.
During WWII and for the next decades, a good number of first-rate musicians had the opportunity to play in what would become the Seventh Army Symphony, which flourished from 1952-1962. Musicians who were not enlisted (for various reasons) were needed to fill the ranks of the American orchestras, so low-paying employment opportunities for competent orchestral musicians were almost plentiful. Musicians from New York made their way westward to places like Cleveland and Indianapolis. I know a bunch of them who returned to New York because they could make a better living freelancing.
As these orchestras became more established, musicians could make enough money to live from their orchestra jobs. Through the second part of the 20th century we saw an explosion of high-quality music making coming from places all over America. Great conductors from Europe made America home, and musical life flourished in many cities. Conservatories produced new generations of employable and employed musicians, musicians and audiences began embracing new American music, and the quality of musicianship kept going up and up.
The 1960s and 1970s were years of great hope for music. Young musicians had options. Some took orchestral auditions (and the good ones got jobs), and some decided to become university professors. The really good musicians who went the university professor route (and you could do it with a Master's degree even in the 1970s) became excellent teachers, and produced musicians who were even more competent than musicians from previous generations. Their students (who required doctorates to get university jobs) made their way into positions at "lesser" universities, spreading the quality of teaching (and music making) out to places that nobody had heard of twenty years before. Chamber music ensembles and chamber orchestras began to flourish, blossom, and record.
The recording biz was bopping during the LP era, but, with the advent of superior recording technology, and the portability of the CD, the recording business magically turned music from an activity into a thing. Something you buy. The term "music industry" started to be thrown around, because people made a lot of their living from royalties from these music-holding things. Now these music-holding things produce little to no royalties for musicians (consider Naxos).
Before the fidelity of recorded music came near to the quality of the real live thing, people would get their musical fun from being in the very place that the music was being played. They would socialize at concerts, and they would enjoy the communal experience. The experience of listening to music has now become largely a personal one, and most of us do most of our listening privately and through earbuds that are wired to devices that hold huge libraries of music.
The amount of music we now have at our fingertips would have blown our minds during the 1970s (and, with all the innovation concerning both old and new music, we thought we had a lot of music at our fingertips then).
We are experiencing a change in our way of life. Classical Music can't be given an imperative to change anything, because it isn't a "thing" that can change. There's no "it."
Those of us who play, write, write about, study, and listen will continue to do what we do, but we will never regain the kind musical life that we (collectively) once had, unless a magnetic force comes close to the earth and wipes out all of our music-producing devices that require electricity. That would put musicians back in business.