This summer’s two biggest entertainment phenomena, the movie “Barbie” and Taylor Swift’s Eras Tour, have a lot in common. Both feature conventionally gorgeous blond women who alternately revel in mainstream femininity and chafe at its limitations, enacting an ambivalence shared by many of their fans. Both, beneath their slick, exuberant pop surfaces, tell female coming-of-age stories marked by existential crises and bitter confrontations with sexism. (The third song on Swift’s set list is “The Man,” whose refrain is, “I’m so sick of running as fast as I can/ wondering if I’d get there quicker/ if I was a man.”) And both have become juggernauts.