Twitter (TWTR) co-founder Ev Williams on Tuesday compared the waning positive buzz around social media to a “sugar high” that’s wearing off.

Williams, who currently runs the publishing website Medium as CEO, drew the comparison during a panel at the annual Collision tech conference in Toronto, Canada on Tuesday. The 47-year-old serial entrepreneur also acknowledged he didn’t have a concrete solution for fixing social media, which has come under fire in more recent years over challenges around data privacy and the spread of misinformation.

“I mean, it [social media] is in the bleakness of figuring out of where it needs to go,” Williams said onstage during his panel on Tuesday. “But I also think the excitement is wearing off. It’s like a sugar high, and now we're like, ‘Oh, do we need this in our life in the same way?’”

Damaged reputations

Since the 2016 U.S. presidential election and the Cambridge Analytica scandal in March 2018 — the latter of which saw up to 87 million Facebook (FB) users’ data exposed — social media platforms have seen their reputations damaged by scandals around misinformation and data privacy.

Social media platforms including Twitter have been criticized for not doing enough to prevent the spread of anti-vaccination propaganda. Which is why in early May, Twitter said it would roll out a new search tool prompting users to head over to vaccines.org. YouTube also announced earlier this year it is demonetizing anti-vaccine videos, and Facebook is downranking anti-vaccine content in users’ News Feeds. Pinterest (PINS), meanwhile, rolled out a virtual blacklist of search terms late last year so that anti-vaccination searches yield a link to the Mayo Clinic.

Such ongoing issues may help explain why social media usage appears to be shifting away from public sharing, possibly impacting Facebook’s and Twitter’s user engagement in the process.

Although Facebook reported an 8% year-over-year increase in monthly active users to 2.38 billion during its first-quarter 2019 earnings, several outside firms have reported over the last year that the amount of time Facebook users are actually spending on Facebook’s site and app has decreased. This April, financial services firm Cowen published a survey reporting the amount of time Facebook users in the U.S. spend on the social network each day had dropped from 58 minutes in first-quarter 2017 to 49 minutes in first-quarter 2019. (Cowen surveyed 2,500 people on a quarterly basis in the U.S. regarding their usage of social media platforms including Facebook from first-quarter 2017 to first-quarter 2019.)