I recently discovered that due to a tiny bug introduced around 3 months ago, I was not getting notified of failures to add new shows to the database. Then, about a month ago, AniDB changed some things in their API, which broke the algorithm used to do exactly that, and I never got notified of this issue because of the aforementioned bug. With the start of the Fall 2019 season, there was a distinct lack of new shows on the calendar, and after receiving some e-mails pointing this out I decided to investigate.
The underlying issues have now been fixed, however no new shows have been added for the last month or so. Due to AniDB API limits, the situation will take a while to normalize as there's a backlog of about 300 different AniDB entries to go through (including OVAs, movies, etc). Fall 2019 shows should start showing up over the next few days (a few have already shown up since yesterday, when the issue was fixed).
Thank you to those people who sent me an e-mail asking about the missing Fall shows, and I'm sorry for any inconvenience caused!