Well-rounded means more than just, say, academic performance, that makes a person stand out. Few average people stand out. How many average people are actually well-rounded? https://www.dictionary.com/browse/well-rounded
About as many as the elites who never get out of their element except for a photo op. I'll stand by my position that very, very few people are well rounded. We just don't get enough real life exposure to others for a long enough period of time in a truly meaningful way to have any real impact on our preconceived notions and ingrained biases we hold.