New York City is a major shopping destination. Variety and prices attract tourists and locals alike into retail stores of all kinds. But legacy brands like Gap or J.Crew are facing a continuing loss of customers.

Marylin is 17 years old, and Gap is a brand she won't buy.

"The thing with Gap is, it used to be good, but now when I buy clothes there, the material is terrible," the teen complained. After one wash, she feels, the fabric feels old and tired.

"With so much to choose from, Gap would be very low on my list," added Marius, who is about 10 years older. "Gap is very generic - it doesn't have identity, doesn't stand out. It's nothing I want to identify with."

Well-known US brands, like J.Crew, Abercrombie & Fitch and Gap, are losing business in the US. They have been relying too long on middle-aged, middle-class customers, who have been content to stick with with classic but stale fashion styles.

Millennials do shop differently

The new generation of customers are the so-called "millennials," those younger than 35. They tend to value good prices rather than logos and status. By the year 2020 they'll be generating 40 percent of retail spending.

"The teens are not shopping for clothing in malls anymore the way they used to," said Herbert Kleinberger, who is an adjunct professor at New York University and a longstanding retail industry consultant.

"Millennials are using their disposable income to buy a lot of other things, like entertainment and electronics," Kleinberger said.

The digital age has shifted a lot of shopping activity online, while also diminishing the importance of malls as social meeting points for youth. The online generation tends to spend their time on other activities and to stay connected through their phones.

California-based Gap announced a few weeks ago that it will close about a quarter of its almost 700 locations in the US. In addition, J.Crew had to cancel its planned stock exchange IPO in 2014 because the company's earnings kept on disappointing. The company has $1.5 billion of debt in its books.

At the same time, overseas competitors keep gaining popularity with US customers, like the Japanese retail brand Uniqlo.

Hype like Apple

"When somebody is wearing a Uniqlo product, it's hard to know it is a Uniqlo product," Kleinberger explained.

Customers today want to be individuals and be different. In the US, "people don't wear things that identify them through the brand as much anymore," Kleinberger said.

When Uniqlo opened its flagship store on New York's Fifth Avenue, the event generated hype on a scale almost as big as when the IT giant Apple releases a new product.

Swedish chain H&M and Spanish competitor Zara are also expanding in the US. The advantage of the so- called "fast fashion" brands is their speed.

"Their supply chain is almost totally vertically integrated," explained Robin Lewis, CEO of The Robin Report, an online retail strategy publication. "That means they own and control almost every ambassador in their supply chain - all the way back to the textile factories and the cut and sew factories."

That allows them to not only control the manufacturing process, but also manufacture quickly and bring apparel more flexibly to the market.

Foreign competitors are twice as fast

It takes up to 9 months for legacy brands like J. Crew, Gap and others to get their products to the market, but foreign competitors are twice as fast. Zara, H&M and others are able to copy new trends from fashion shows worldwide within a few days.

In the case of Zara, Lewis said, US stores are in contact with the headquarters in Spain on a daily basis.

"They take all that information coming in every night," Lewis said. "And they're constantly creating small new lines that they ship into their stores."

Sometimes, this means every two weeks. These lines are small enough to allow the company to quickly get rid of apparel that isn't selling.

Whether it's H&M, Uniqlo or Zara - many foreign chains are growing and grabbing market share in the US retail market. In mid September, Irish apparel chain Primark will join in the fray: It's opening its first US store in Boston, and more locations are planned.

In the meantime, traditional US brands are working on a makeover. J.Crew is trying to target price-conscious customers with its new daughter company, J.Crew Mercantile. Gap is also trying to bring smaller lines into the shops of its own subsidiary, Old Navy, so that it can react more flexibly on trends and get a better sense of what customers want.