A big plagiarism scandal could not only rethink artistic authenticity but also validate it. While the attitudes towards not writing your own songs would change (especially when it’s done on the basis of avoiding plagiarism), the attitude towards inauthenticity won’t. It’s found a more appropriate target.
By then, not writing your own songs is optional especially if it were either from a pre-existing catalogue readily used by choral groups and the like without fear of plagiarism, cover songs or public domain. You’ll find many more folk-pop crossovers in the 2020s because of that very fear.
What is forbidden is plagiarising stuff, especially if it’s copyrighted and can’t be stolen by anybody else without permission or something. Plagiarists are practically inauthentic in that they’re never the real thing. They’d be deemed as manufactured as the lip-syncher.
They’d be even regarded as manufactured as the musician that doesn’t write its own songs formerly was. Which is saying because the bar for musicianship is higher than before. Higher still if it includes the legal or ethical dimension.