Musicians not writing their own songs has been a thing though a precisely bigger issue at this point wouldn’t just be whoever gets the real credit but also whether if they’re plagiarising from somebody else. Should a big plagiarism scandal occur, it could raise the bar for musicianship.
So it’s not enough to write your own songs but also come up with your own ideas or otherwise you’d be better off using the public domain instead. That’s also the only situation where somebody can get away both with not writing their own songs without being caught plagiarising and doubting its artistry.
Having popstars sing cover songs isn’t a bad thing and some often do it but that’s ironically more authentic than plagiarising somebody else’s song. At least they’re just doing their own interpretations of somebody’s words and lyrics instead of stealing it.