I'll give you my take on this but it's just my personal take: I think you're right and wrong—right because HN does go through these waves, but wrong because it's a fluctuation process that stays fairly steady in the long run. (At least we're determined to keep it so, if we can - https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...)

That's why people have been experiencing this "HN has gotten a lot more $BAD-QUALITY recently" since pretty much the origin of the site.