>What about X generations later?
X generations later the number of possible mutations are so big you'd be grasping to point at this as 'the' moment Reddit messed up, unless the statistics clearly indicate it (at which point you can still argue against it). For each person like you who said 'this API change was the moment things fell apart', you'll get another pointing out Reddit mobile, new Reddit, spez becoming CEO, the other incidents they scapegoated onto someone, and more.
Even now, people could argue the worst thing happening isn't the mods being replaced, but Reddit allowing mods to put popular subs on private. The way things are going, those two events will be so close together they'd be practically indistinguishable in the grand scheme.
>As for the UI change. That's a completely different topic and I am not sure why you are bringing this up.
No it's not. It boils down to the same thing: UX experience degradation. Redditors have been on the receiving end of UX degradation for more than a decade now. Your whole argument relies on new moderation making UX bad enough to drive users away.
>And I am predicting the mod (thus content) quality will eventually be significantly worse
Great, like almost everybody, nothing new. Only difference being, you set your forecast on 'in some day in the future' now, which wasn't at all clear from your OP, rather than 'this is the event that will kill Reddit in the next 3 months' everybody is proclaiming it as.