There is no doubt that The Coppola family gene is infused with above-normal talent. Gia Coppola’s sophomore effort as director, “Mainstream,” doesn’t reach the deeper level of her first film (2013’s “Palo Alto”) but she and co-writer Tom Stuart’s screenplay has a lot to say.

Frankie (Maya Hawke) is a young woman on a journey to find herself in an artificial world. She works in a dive that features