Digg died basically overnight after a redesign. It happens.
Someone else gets to reap the damage they have sown. But engineers do the same thing.
In this case, Snapchat just seems to be copying feeds to make money. And Wall Street is breathing down their necks.
What makes it difficult that even the most perfect change will elicit negative reactions from users. It's difficult to then separate what is a natural reaction to change from genuine problems in the new design.
If you have a moat, you can weather the storm after a design snafu. If you don't? @Jack, you dead.
Seems to be the trend of the last 5 years of making the desktop experience broken/annoying in some way or form and the mobile experience - ad-ridden and designed for momentary rather than deep engagement.
There have been attempts to do something else, such as voat, but those generally become either A) more akin to subreddits than reddit (like this very site) or B) ideological havens for groups not welcome on reddit.
In voat's case, when reddit begin banning overt racism from white supremacists and calls for violence, as well as communities dedicated to hating fat people or women, those radicalized users all fled to voat. That toxic core userbase makes the site untenable for the masses who are repulsed by such naked racism, prejudice and other evil content.
So I don't really see anyone waiting in the reddit wings. The ones that were there before are still there (SA, fark, /.), and the ones that follow aren't poised to be the same thing.