from my perspective, it's relieving to see that the number of users has remained mostly constant in recent years. of course it's selfish to think in this way, but almost no "social media" or UGC-based platform that i've used has actually become better or more useful to me as it became (much) larger.
this kind of fast growth in users (beyond some size) often leads to a shift in the culture that made preexisting users participate in the first place, leading to a loss in overall quality of the platform as a whole. if the growth is gradual enough, then new users eventually figure out how to fit into the culture or leave.
i guess i've said nothing that isn't obvious to people who have used a computer before, basically "yay no eternal september for HN yet", but i digress.