Yes, it's primarily a portrait of the challenges a young woman from Ireland faced in truly leaving home and family, and finding her path in New York City, not without some twists and complications.
(And see Richard Brody's critical review, in which he observes, "But if Brooklyn greenwashes Ireland, it utterly sanitizes Brooklyn.")
But what was astounding, for contemporary observers of the borough, is that the boardinghouse that young Eilis Lacey lived in was a brownstone on Clinton Street. (Google Books tells me no address is listed, and Clinton Street is mentioned exactly twice.)
Clinton Street today runs from Carroll Gardens through Cobble Hill, then across Atlantic Avenue into Brooklyn Heights. Presumably Eilis and her beau Tony were walking around the part that today is called Carroll Gardens but back then was just undifferentiated "South Brooklyn," before new residents and the real estate industry pushed for new names.
Back then, it was a working-class zone. Today, those brownstones are very, very precious.
By the way, according to a Crowley interview with Deadline Hollywood, they shot for exactly one day in the brownstone district and one day in Coney Island, with the rest of the shoot in Montreal to save money!
Here's another relevant Crowley quote, from Brooklyn magazine: "Modern-day Brooklyn is so different from 50s Brooklyn that the art department budget would be astronomical."