Apple, Google and Amazon have had a great 2017 so far, but the companies investors should be paying attention to aren't even public yet, Aspen Institute CEO Walter Isaacson told CNBC on Monday.

"It's surprising that this entire tech boom in the past few months has really focused on the big companies," Isaacson said. At some point that focus should shift to up-and-coming companies like Uber, he said.

"I think it's indicative of something larger that we should keep an eye on, which is the pace of wholly new innovation which seems to have slowed down," said Isaacson.

GGV Capital managing partner Jeff Richards agreed.

"We are seeing a huge boom for the large-cap tech stocks. But don't count out recent IPOs. The IPO class of 2016 is up 48 percent to date, and IPO class of 2017 is up 17 percent," said Richards. He said the positive market reception to new offerings is a good sign for private companies that are planning to go public.

"There is an undercurrent of up-and-coming companies, and beyond companies like Uber and Airbnb, you have great tech companies that are still private like Houzz, Stripe and Dropbox," said Richards. "They ... aren't really on the public market radar yet but will be over the next 12 to 18 months," he said. "We think that's a healthy undercurrent."

Correction: Aspen Institute CEO Walter Isaacson spoke to CNBC on Monday. An earlier version misstated the day.