>>509876446 (OP)A transition happened in the 90's, brought on by television and MTV; where image and presentation became more important than music. So they'd take someone who can't sing; put them in flashy costumes for the music video; and then hope to piece together enough takes to make at least one workable version of a song for release.
This compared to the 40's and 50's; where someone just stood there to sing; and if they looked good that was just a side-benefit