As a Young People™, this is not entirely true.

Stories are only partly chronological. The stories are grouped per user and in these groups they are chronological. However these groups are not chronological.

Secondly, posts are not for old people. Posts serve a different purpose than stories. The barrier to post is a lot higher, and they are definitely not used (anymore) to share that you are going to a restaurant/movie/etc, because stories took over that niche. However something like a (single!) post with (multiple) photos of your last holiday (with at least the first one including you) and some fun caption is still totally done.

Hell, im a pretty early adopter of instagram along with loads of friends and like 95% of content has become stories.

Turns out Snapchat was what most of us wanted but without a purposefully obtuse interface

I liked Snapchat, but I don't like stories. To me, the beauty of Snapchat was that I could share a funny moment with a couple of friends who I thought would find the same thing amusing. I can't do that with stories. It's like being forced to tell a in-joke to all of my friends at the same time. I'd rather just not tell the joke at all.

You can have a "Close friends" list or multiple accounts. Neither is particularly UX-ergonomic, but that's what people do to address that need

The fact that they succeeded in spite of a purposefully obtuse interface is a pretty clear validation for the concept.

I think the general belief was that the concept was a thing for "kids"/"young people", but now I'm very convinced that that was because of Snap's branding + general incomprehensibility.

Did they really succeed though?

They succeeded enough to scare zucc into war mode.

Snapchat's main problem was the default screen was full of tabloid magazines from a grocery store checkout aisle.

Give it a year or two and I bet there will be unskippable ads between the stories.

Worth noting that “very young people” are using TikTok and Instagram is usually an afterthought for them.

If you’re a big insta user you’re already “two generations” out of date (snap and TikTok).

Stories are not chronological.

Most people under the age of 30 are using Snapchat

Single European datapoint, I'm currently in university.

In my country we have different levels of tertiary (?) education, as far as I can tell, lower levels of education have way more Snapchat use than Instagram. For most students of higher levels Snapchat is only used to share your night out with friend groups, but pretty much nothing else, while Instagram is used way more.

Not the case at all.

True here - the only people I use anything else with is work colleagues and parents. Everyone else uses Snap.