>nobody is out there lamenting that we're not supporting a 'middle class' of baseball players.
I will cheekily argue that the "transferable skill" of failed athletes is charisma. It's pretty clear that being able to talk about sports is a cheat code for upwards mobility (no matter the industry) and the mentality it builds is of high social value (you'll never find trouble finding a local court or field to make a pickup game with. An artists Meetup, a bit harder to arrange). Certainly more than 99% of artists.
But to properly answer your point, I don't have the full answer of how to balance "necessary careers" with "dream careers". If you want to maintain a satisfied populace (aka, prevent a violent coup by people who feel they have nothing to lose), they need to feel their dreams are reachable. Emphasis on "feel".
You don't even need to make money off your dreams per se. But you need time for it, and basics safeties taken care of. the current atmosphere offers neither.