I think "common culture" is precisely the problem with reddit. Before reddit there were many different separate forums. Each had to be signed up to separately and each had their own culture. With reddit there's little barrier between reddits, which has lead to a shared culture across the whole site. The culture is generally friendly, but is immature and superficial. It's great for small-talk, but useless and frustrating if you actually want to learn something.

Maybe I'm bitter, but I used to really enjoy r/rust up until 2 years ago or so. Now it's completely inane and it's no longer worth the time to sort through the noise to find the signal.