Just a personal anecdote but I have tried installing Snapchat app on my iPhone about a year ago or so. I have spent about 20 minutes tapping and swiping around the app to try to figure out how to use it. I couldn't get how it works and was so frustrated that I have uninstalled it.
In addition to UI being most confusing and impossible for me to figure out, it was also super slow on a mobile network in Asia where I was at the time, near unresponsive.
If I, as 25-30 years old tech person cannot figure out how to use your mobile app, you got a problem. I completely understand why the user base growth has completely flatlined. I assume there are a lot of people similar to me.
I am very bearish on Snap.