I've spend hours upon hours with Algolia on several years old HN threads. I don't know how you come to the conclusion that it was better back then. Lots of threads had replies that would get light light grey real fast these days - not because they were controversial, but they just didn't bring any value to the table.

Edit: Something that came to my mind right after hitting 'reply': Maybe the share of technical threads to political/ psychological/ religious/ philosophical/ news/ etc. threads was bigger in comparison... If that's a downgrade for you, then I could understand your position.