Kohlchan is basically the end result of all the long-term trends that were slowing killing old KC - pedos, low effort shitposting, endless discussions about sex and relationships, a million variations of the same flavor of the month news thread.
There was no golden age of serious discussions, but old KC did have the best sense of community of any imageboard ever, until about 2015. I even met my now ex-wife at a Bernd meetup in my city.
It makes me sad that we'll never have that back, but I guess the age of imageboards is over now anyway.