As second in command to J.Crew’s CEO, legendary merchant Mickey Drexler, Lyons was in charge of all product design, visual and brand presentation, and of J.Crew’s overall aesthetic. But after a five-year stint in that job, it was clear Lyons had lost her Midas touch. Comparable sales at J.Crew fell 6.7% in the fiscal year that recently ended, on top of an 8.2% drop the year before. What’s more, J.Crew’s private equity owners, TPG Capital and Leonard Green & Partners, took a $1 billion write-down in 2015 because of the brand’s deteriorating popularity (and of how much they overpaid for the retailer).

“She has made many significant contributions to J.Crew and has built an incredibly talented team,” Drexler said in a statement. “J.Crew is focused on continuing the progress underway as we execute on our strategic initiatives and position the Company for the long term.” In an interview with the Business of Fashion news site, which first reported the news, he said Lyons was leaving by mutual agreement.

Lyons will stay on as a creative advisor until December 2017 before leaving the company altogether. She joined the company in 1990, and helped turned J.Crew into one of the most popular fashion chains, offering relatively affordable clothes with a preppy but quirky sensibility. Such was her success that she became president in 2010. Over the years, designs like her pencil skirt, as well as her own unique personal style with its emphasis on enormous glasses and jewelry, made Lyons herself a fashion icon.

More recently on her watch, there were fashion misfires, and uneven quality that tested the devotion of J.Crew’s legion of fans, particularly women. On top of a string of uninspired designs, J.Crew proved no more immune than rivals like Gap Inc. (GPS) and Abercrombie & Fitch (ANF) to challenges like shoppers’ shift to discounting, the pressure from fast fashion chains like H&M and Zara, and overall boredom with the abundance of fashion options.

J.Crew has tried to right the ship with a return to some basics, and with initiatives like a move to open some J.Crew boutiques within Nordstrom (JWN) department stores. But those revival efforts have been to little avail so far. The only bright spot currently in J.Crew’s financial picture is the growth of Madewell, the company’s hipper, artier women’s denim chain, which is a much smaller business than the namesake retailer.

Lyons’s position of Executive Creative Director will be eliminated. But J.Crew women’s head of design, Somsack Sikhounmuong, who had earlier overseeing Madewell’s design, will become chief design officer, and oversee all design teams, effective now.

As for J.Crew, it must figure a way back into shoppers’ graces at a time nearly all clothing chains are struggling, even as its heavy debt load is choking it. A good chunk of its $1.5 billion debt comes due sometime in 2018, an enormous load to carry for a company with barely over $2 billion in annual sales.