Excellent article, and I quite agree with your thesis. The decline of audience in broadly-based blogs seems to be very clearly attached to both the rise of social media and the prominence of streaming, to the detriment of more engaged and thoughtful discourse.
It’s a bit like gaming… When word processors were first introduced, I marveled at how ordinary people were having to learn something about fonts, but they eventually mastered the skill. With social media, people are learning that they are rewarded for certain kinds of attachments, certain kinds of quick jokes or replies, and that’s what they’re learning.
The rewards of actual, rich content are less immediate. You always get more of what you reward.