Another statement I've seen in the comments is that there haven't been as many "daily writers" in the past, meaning writers who post every day. It has been said that people used to spend more time commenting than writing posts.

I think that is not true. Back in the early days of Steemit, there was a lot more "garbage" posted here and definitely not more comments, at least now I comment a lot more. And a daily post is exactly the optimal norm for active authors, which does not allow clogging the feed. There were times when I used to publish four posts a day and they were definitely not of the best quality. However, this is because I was afraid to publish in my native language at the time, and the translator was much less perfect then.