This might be true but I finally deployed nextcloud for our co-op because I couldn't find any other solution to easily have a shared calendar with granular perm

This might be true but I finally deployed nextcloud for our co-op because I couldn't find any other solution to easily have a shared calendar with granular permissions to accounts I assign for write privileges, but also a dynamic ICS file download endpoint I can publicly expose. I tried a couple other caldav servers and none had this. So it does at least one thing better than specialized apps, which I typically prefer to use.