I really like snapchat because it is super casual and there is no inherent risk in throwing something goofy together, and no pressure of getting likes or upvotes or anything.
Facebook is where your relatives are, and Instagram is where your entire peer group is. Snapchat is where you can share with who you want (send private snaps to groups, and post stories to the public) while still seeing everyone's content. All while being reasonably confident that your photos/videos aren't being saved (or at least notified when they are, assuming somebody doesnt have an external camera ready).
All of that, plus the ads just feel fair. They exist, appear at the "right" times, and can easily be skipped if content isn't interesting.
I used to think snapchat was a fad. But as its evolved, I've become increasingly confident in their ability to stay relevant.
Edit: I didn't awknowledge your "no like count" point - also spot on. Only visible metric is views to your story, and that isn't public. Pressure to post something "amazing" just doesn't exist like other social networks.
Partially because we're doing long distance at the moment, but a lot of it has to do with how fun the filters are—and they're always changing them, too!
This is what happens to all social media platforms in time. Young people don't want to be where their parents are. Then the parents arrive. Then the young people leave. It's a constant cycle.
I won't dispute your other points, but I wonder, since skipping the ads is so easy, does anyone ever NOT skip them? I know I certainly have never watched one voluntarily. I also know that I'm a bit of an outlier when it comes to that sort of thing, but I really can't think of any good reason why people wouldn't just skip them every time.