Never had an issue with caldav and cardav. Maybe you are using broken servers or clients?
Even notes can be done efficiently on those standards…
But, hey, I am using only FOSS server and clients, maybe you referring to proprietary ones? You know, those who are mare by vendors who have no interest in interoperability?
Gentoo linux with Radicale on bare metal. Radicale is behind NGINX reverse proxy that slaps HTTPS and authelia redirect for authentication on top.
And of course i use DAV5X on android.