If you use the app all the time it's easy to keep up with the changes, Zhang explained. But it's hard for older users to memorize the pinching and swiping motions to use the app.
"It's hard for new users to jump in, like my mother," he said. "She tried it for a day, and gave up because the UI (user interface) is not so intuitive."
Zhang noted he has an iPhone, but the app doesn't work as well for Android users. Snap said during its latest earnings report that it is working on improving its Android experience. If it does, Zhang thinks the company will add users in regions where Android phones are more common, such as India.
But even Smith, who uses Snapchat, finds it difficult.
"(Snapchat), at least to me, is not exactly user-friendly," Smith said. "Sometimes I have to remind myself how to get to certain areas that aren't just a left or right swipe."
Snap is addressing this issue by revamping its app, reportedly in December. The new version will have a feed inspired by Twitter and Facebook.
Still, it may be too late for people who have already migrated to Instagram. Smith said he checks Snapchat every few days but has migrated mostly to Instagram Stories. He already uses Instagram and more of his friends are there. Plus, a lot of people are uploading their snaps on Instagram Stories anyway.
"I really can't be bothered to go into Snapchat to watch the daily stories," he said. "I just went in to look at Snap stories, and there's loads of advertisements that overtake the screen, which just looks like the tabloids when you are in the grocery store."