Snap's UI is horrendous and it has nothing to do with ads. Kids can invest innumerable hours to find and utilize all the hidden ways to interact but your average adult is just going to do the basics and will put it down.

That's fine. Kids are often the market these social media companies target as they launch anyway.

I've never seen a single ad on Snapchat. Where do they even show up?

I'd agree if those tasks were part of what they were planning to be a part of the app experience - but seeing as they're explicitly not, then from a pure design perspective, the UI is perfect in that regard.