Studio musicians used to make a decent living, there was one group of them, the Wrecking crew in LA, that were legendary. Likewise, the session musicians who did movie work made a pretty decent living. They still exist, but between synthesizers and offshoring soundtrack work to places like Eastern Europe, it isn’t the same as it used to be, in LA there is a small group of musicians who do film work , and it is like a guild, when someone retires a student of theirs takes over. There have been a lot of working musicians who make a living out of gig work, filling in at theaters or with orchestras, weddings, other kind of events plus teaching.
It is why schools teach entrepeneurship and talk about ways to make a living . In Chamber music the goal for many groups is to became the group in residence at a school, where they teach (and get benefits) to use as a base for touring. I am sure there is a lot of other ways out there to make a living as a musician. And obviously, there is still if you get lucky enough to hook on with a decent full time orchestra, that route, where you have salary and benefits, and then you also can teach, do gig work of various sorts, etc. The problem is the number of full time orchestras has declined, and the competition is much, much stronger than it ever was.