I haven't looked at 4chan in ages, but my conclusion was trolling by smart people evolved in to ideas enthusiastically spread by dumb people. You can see evidence of this in the anti-vax community where the line between devious trolling and just really idiotic behavior is.

A better analogy for Snapchat and UI design is fashion. Fashion is basically an invisible circle of inclusion. Clothing styles don't go out of fashion because they are old, they go out of fashion because people outside of the circle begin to wear them.

There are arguments here about about gatekeeping or whether changing UI conventions are good or bad. There is some parts of truth to all of this.

I would make an important distinction. UI/UX design can be quantitatively good or bad. It is measurable if UI sucks or not. That measurement can be, perhaps mistakenly, only taken by new users: how fast did they learn the UI? I would argue it's the advanced users which are more important: how much can an experienced user get done?

To make matters more difficult, most of the UI design we are experiencing is commercial. It is, in fact, not there to improve our output, it's there to make their owners more money. The move toward cloud software has really fucked up the UI/UX of stuff that worked for a long time, like Photoshop. New stuff is continually introduced breaking known workflows.

On the business side I was always very pro-active about building our tools and systems on open source software or at least in a way we could always easily migrate our data to something else. Now I'm in the process of doing it on the personal side. I have minimal interest in using new tools that aren't interoperable, that I can't control the UI/UX workflow. Even something like Signal, that should be open source, really falls flat on this one. Imagining using something (like Snapchat) where the UI is going to switch so they can increase their engagement and increase ad revenue is just horrible. Internet users don't deserve this and don't need it.

Edit: hn's UI is fantastic, and a major reason I'm still here many years later (I don't use reddit)