Anecdotal obviously, but I’m barely outside this demographic at 22. I can tell you that nobody around my age in NYC uses snap anymore. In fact, it’s looked at with shock or disdain if someone mentions that they opened it for one reason or another.
Social media company perceptions are skewed by hype cycles. For instance, snap has more DAUs than Twitter (plus bots likely inflate Twitters numbers more), but everyone talks about Twitter as if it's a giant that everyone uses. It's important to look at the data sometimes, and not just high profile drama.
Moved from PR to WA for a couple months to intern alongside others my age. Everybody used Snapchat. It was the group message app of choice.
Back home, people still use it for keeping up with close friends via stories and whatnot. And, y’know, the other stuff Snapchat is great for.
So if Snapchat stopped existing tomorrow they'd probably move to iMessage. Until one of their friends gets an Android.