This trend has been established since the mid sixties. Marshall McLuhan pointed out that technological changes to media do more to alter society than the content transmitted or created by those media.
1. Ease of use --- we've gone from a web where minor coding skills were required to produce readable content to where the only mental labour required is installing an app, signing up for an account and then thinking a thought. Many people don't even really do that last step and just rip off other people. Even during the livejournal days integrating graphics into a text post was cumbersome and video hosting was a pain in the ass. Beyond attracting a more dedicated and educated audience, forcing users to perform that extra work creates time for people to think over what they wrote. Whenever I wrote a post, I almost always added some nuance while fiddling with the BBcode or finding a picture to hotlink to.
2. Incentive of feedback --- This change is a lot more subtle, but larger web audiences mean that it's a lot easier for anyone to make a post that is seen by a large audience. This is made potent by content integration, both within and across platforms. Your Google account is connected to your Facebook account which is then connected to your Twitter, Instagram, etc. This all makes finding the content you want easy, and makes saving and sharing easy as well. Meanwhile we also get instant response metrics in the form of likes, reblogs, retweets, and so on. Even 4chan has an indirect like function in the form of (You)s and links to replies built in to a post. All of these responses give us little shots of dopamine, wants us craving more (You)s. Remember when the site administration tried to remove (You) from replies? The site threw a conniption fit and they put it back.
All of this combined allows even the most normal of neurotypicals to figure out what posts people want and then alter their future posts accordingly by finding such content without much effort. Usually by making more lewd posts or shitposts, since people are attracted to controversy or polarizing opinions or titties.
Is this all bad? No. The insular web communities of yore were also prone to constant drama and web 2.0 has cut down on that, mostly by just drowning out drama in a sea of content.
I don't think it really means much, since people who are dedicated still exist. As long as they are mindful of web 2.0 background static they can still have informative conversations.