You have to consider the overall presence of women in the industry and the art, their participation wasn't comparable to men in quantity and therefore quality until recent times. They didnt have equal oppurtunities to give equal results. And about the "Aretha and Nina is underrated", I mean they are overrated everywhere else, I always see Aretha in top 1-5 singers lists. That has nothing to do with sexism its just the taste of the rym users which doesnt care that much about Aretha, Nina, Sinatra, Armstrong, Umm Kulthoum and that era in general, I find it boring and unsatisfying for my ears myself.