To be fair, the role originated with Mandy Moore, who basically only did pop music, so it’s not like the role requires significant, stage theater level vocal chops to do the songs justice. In fact, not being the most proficient singer and having a bit more of that girl-next-door quality to their voice is kind appropriate for someone like Rapunzel who’s been locked and cooped up and kept hidden in a tower all her life.
She shouldn’t sound like a trained thespian. She should sound just like a person with slightly above average vocal talent.