Reddit's rise to prominence is in part a result of emphasis on facilitating the discourse Facebook used to be a place for. Facebook as a venue for discourse has gradually ended over the past decade or so, for the majority that still use it it is now just a centralised email server for sending event invitations.

No one has global Reddit traffic data except for Reddit - market estimation methods can't really account for a deviation from the norm on such a short timeframe. Regardless, it's the users that matter that are gone, we agree on that. The same ones that made Reddit the safehaven for Digg users to begin with.

I don't think Reddit is going the way of the Dodo, it's Reddit as a platform for discourse I'm on my soapbox about. Probably the largest exchange of ideas in human history happened on it. But the writing is now on the wall, to continue posting you first need to overcome the internal conflict of putting stock in a platform whose killer use case was predicated on user goodwill now burned. That itself is enough of an obstacle to make folks disengage, skewing the userbase, post quality declines, and then it's just another cesspool. All of this takes time though