[GFischer]

Adding to your point of "huge influx of new users", that's called the "Eternal September" effect, after a time where Usenet was flooded with AOL users and they destroyed that culture:

https://en.wikipedia.org/wiki/Eternal_September

Interestingly enough, some time ago HN did a study of what new users upvoted compared to old-timers, and the deviation wasn't significant.

You can compare the current front page to the "old-timers" front page by visiting HN Classic:

https://news.ycombinator.com/classic

Edit: pg's post where he mentions the lack of a difference

https://news.ycombinator.com/item?id=607271