Evan Spiegel has made great products at Snapchat. Growing them has been harder.

Snapchat suddenly has a product problem.

CEO Evan Spiegel announced last week that Snapchat is getting a redesign because it’s “difficult to understand or hard to use.”

His decision to rebuild the app just nine months into Snap’s life as a public company has led some to question whether or not Spiegel is truly the product savant he’s been made out to be. When I profiled Spiegel last spring, those close to him likened him to a Picasso — an extraordinary claim, but also a nod to his ability to create stuff no one else could.

The problem is that Spiegel is not just an inventor. He’s the CEO of a publicly traded company. This means that his success is measured by metrics like user growth, revenue and profit, not by the novelty of his latest creation.

Spiegel is great at coming up with creative and unique products. Disappearing photos and videos? Awesome. Opening the app directly into camera mode? Novel. Pioneering the push into mobile-native vertical video, and vertical video advertising? It’s changing the way some of the world’s largest content producers are thinking about their business.

Snapchat was also one of the first to push augmented reality into the mainstream, with goofy face filters and cartoon avatars that will dance on your kitchen table. Even Spectacles, the video-recording sunglasses that were much flashier than they were practical, were at least fun and interesting.

They just aren’t necessary to enough people — or defensible enough to prevent copycats. Snap’s product problem is a problem of scale and utility, not creativity.

As a digital advertising company, Snap’s business is dependent on getting a boatload of users, which in turn means it can show those users a boatload of ads. Snapchat has 178 million daily users, so it’s far from small. But six years after its founding, Snapchat’s user growth has slowed.

One of the reasons seems to be that Facebook has copied many of Snapchat’s best features into lots of its products, most notably Instagram. Snap’s user growth slowed dramatically in Q3 2016, the same quarter Instagram copied Snapchat’s Stories feature.

It’s tough to blame Spiegel for Facebook, and it’s tough to invent products that Facebook can’t quickly replicate — and with almost 1.4 billion daily users, quickly dominate.

It’s easy, though, to blame Spiegel for failing to grasp the importance of scale when trying to build an independent digital advertising business that can hold its own as a public company. At the time of the IPO, Snap’s philosophy was to focus on select markets with higher-end smartphones instead of aiming for broader appeal.

Despite a general consensus that Snapchat was too hard for many people to understand — its difficult-to-navigate app became something of an identity, helping lure younger, mobile-savvy users, at the expense of mass adoption — Spiegel refused to change. Even as Snapchat became a buzzy cultural phenomenon, those who used it weren’t able to easily find and connect with their friends, which probably stifled some network growth.

So, yes, Snapchat suddenly has a product problem. Its core app doesn’t appeal to as many people as Wall Street would like. And because Spiegel pushed Snap to go public so early in its existence, Wall Street isn’t something he can simply ignore.

This is now a personal challenge for Spiegel, who is not just CEO at Snap, but has the final say on almost all decisions, especially product ones. He chose to narrow Snap’s focus, which seemed smart at the time. Now he has the tricky problem of changing his thinking — and Snapchat’s user experience — on the fly to make it more friendly to new users without alienating his old ones.

This article originally appeared on Recode.net.