Here's the real problem with start-ups, says Walter Isaacson

Creative tech start-ups face a daunting task in expanding to scale, Walter Isaacson said on Monday.

That poses a bigger challenge to the sector than a private funding bubble some prominent investors recently decried, the Aspen Institute CEO contended.

"I think the other conversation here is not that we're in a bubble. But we have a lot of start-ups. How do we accelerate them? How do we make them scale?" Isaacson told CNBC's "Squawk Alley" from the South by Southwest conference in Austin, Texas.

Read MoreCuban on the tech bubble: There's no liquidity

On Sunday, investor Bill Gurley told conference attendees that a run of huge private tech valuations could soon end, adding that venture capital firms have "no fear." His assertions follow investor Mark Cuban's recent claims that a private bubble exists worse than the tech stock bubble that burst in 2000.

Walter Isaacson
Adam Jeffery | CNBC
Walter Isaacson

U.S. start-ups have larger issues than huge rounds of private funding and overvaluations, Isaacson said.

"The real problem is everybody has a great idea. They all want to do a start-up like Mark Zuckerberg in a dorm room. They haven't really thought through—what if there are a thousand apps and services doing the same thing? How am I going to stand out?" he said.

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Start-ups promoting similar products and ideas are scattered across the country, Isaacson said. He noted that many "interesting" ideas remain "very local."

He also said that consolidation of services could help start-ups take their ideas to scale.