Here's the thing, I don't think these careers should be the only options, but the door shouldn't be closed on them either.
If your child has a natural talent and love for music, why push something else like math or science on them? Especially if they're mediocre or average in that regard?
If you think it may be the school system, then either switch schools, do homeschooling, hire a tutor, and/or put them in one of those after school programs that encourage the development in that area. If they thrive great, it was on the school. Make the adjustments and raise them with a balanced education. If they still aren't doing that hot and don't have any kind of natural talent in anything apparent you have to encourage them that they have to work harder at it. Effort is transformative in that the more you work at something, the better you get at it. Encourage your child to do the harder problems and not just settle for a bunch of easy stuff they've already mastered. You have to encourage their growth and instill in them the reason why they're doing good is because of their work ethic and natural ability means nothing (although you know it does). This way they'll have a much higher floor and will most likely at worst have a college degree.
However, as stated if they have a real knack for music/arts that is very apparent over some subjects they're only average at best at, you must follow through on it and I'd personally stop all extracurricular activities in other subjects and put more emphasis on their natural gifts. People follow their passions late in life and do great, but the one thing that's also common is them saying they wished they done it sooner.
Afterall, cats like Prince probably really don't care that they're not engineers and scientists and wouldn't trade places with one either.
Remember, ditching one extreme for another as a collective means there's going to be abundance in one area and absence in another. Switching to education is a great thing, but that'll mean no presence in the entertainment industry as well.
Don't be shamed out of your natural advantages, that's vital.