iOS used to be an absolute pain in the ass. Had to scratch my head for several days a few years ago. I believe it was iOS 15. Forcing SSL and self-signed certs with some odd flags finally did it but it was not straightforward. Good luck reading logs on an iPad. Unfortunately I don't remember any specifics.
Other than that I've had zero issues with Baikal for the last couple of years. Roughly 15 devices (iOS, Android, Windows, Linux), and 5 users each with multiple calendars, tasks, contacts, notes etc. and everything just works. DAVx is excellent if you use Android as CalDAV isn't natively supported for some reason.
But I get your point. CalDAV as a standard has always felt a bit... Janky? It never left the early 2000s. So setting up a CalDAV server in 2024 isn't particularly difficult but everyone wants their own implementation. And your server/client combo probably require you to find some obscure forum post from 2009 and reading the man pages several times before you find that one specific fucking legacy parameter in some config file that has to be set.
You could always set up your own Exchange server though if you're a true masochist.
I remember the opposite - the discussions on Reddit had some quality threads with depth and actual knowledge. Someone would post a pic of some random ebay haul and they would receive 10 replies suggesting what they should have gotten instead, along with 18 bullet points explaining why.
The threads here are either people asking how to set up some crappy *arr service on their first raspberry or why god created Jellyfin on the seventh day and not the first.
I've been waiting since the exodus for the quality to increase here... Still hoping.