You are getting down voted for your sweeping generalizations, but I agree Reddit has declined in quality over the years. So has HN. 4chan has also declined some

You are getting down voted for your sweeping generalizations, but I agree Reddit has declined in quality over the years. So has HN. 4chan has also declined somewhat but its brashness serves as a filter and is a barrier to entry for many people. People who have been around 4chan for a while know the offensiveness is essential to preserving the culture.