Does anyone know why there’s no desire to see a working standard (protocol) for calendar/tasks?
It’s clear that CalDAV doesn’t function consistently across devices (and does seem to be dying as a standard). If you work across different devices/OS it’s virtually impossible to get things set up seamlessly. Companies and developers of task apps seem happy to create silos and not look at interoperability.
If you want to self-host, it’s too hard to do this and you really are limited to a tiny number of options.
It’s more than the “proprietary apps”. It’s harder than it should be to simply sync calendar and tasks. The one that seems to work the most effectively is Nextcloud. By now there should be straightforward, easy to use (to host) solitions that just work.