This has nothing to do with the new design. If Reddit was ever a place for “serious, well thought discussion”, it hasn’t been that way for the past 10 years.
That's just for work related things. In terms of having conversations about relationships, or sports, or new phones and tablets, I wouldn't even think of having these anywhere but Reddit.
Granted, I don't spend time on r/pics, or r/teenagers or whatever is on the front page. But I don't click the "Trending" tab on Youtube either.
I only recently started reading HN after many years on Reddit, and even though a portion of what gets posted here is too technical and techy for me, I truly appreciate the thoughtful nature of the comments. It's quite a relief just to communicate with people who seem basically sane, mature, and intelligent.