The reminders app loses its ability to be adjusted via CalDAV after an update to the new version.
CalDAV is an established standard that allows you to synchronize calendar information with other calendars, so no matter if you enter something in your Google Calendar or on your iPhone, both calendars understand each other.
Apple has now given the reminders app a few new functions. These new features are no longer covered by the CalDAV standard and so the app will ask if you want to update. We already showed you here that you’ll lose all compatibility with older Macs and iPhones.
New features vs. CalDAV compatibility.
This is also a problem for third-party apps such as BusyCal: they have also obtained their information via the CalDAV interface. So if you update the Reminders app, then the third party programs are also out – here you can read the detailed problem description.
To make a long story short: Do you use the Reminders App only in the Apple ecosystem and have only devices running under macOS 10.15 Catalina or iOS 13 you can update the app. If you have any Mac or iPhone/iPad that has an older system you should let the update stay. The same applies if you want to have access to your reminders via CalDAV.
