Sooooo why not just host any caldav server instead? Like, why is nextcloud so popular compared to self hosting caldav?

In my case, I want file/photo syncing, calendar syncing, and contact syncing.

Nextcloud provides all 3 in a package that pretty much just works, in my experience (despite being kinda slow).

The Notes app is a pretty nice wrapper around a specific folder full of markdown files, I mostly use it on my phone, and on my desktop I just use my favorite editor to poke at the .md files directly.

Oh, and when a friend group wanted a better way to figure out which day to get together, I just installed the Polls app with a few clicks and we use that now.

I am a bit disappointed in the performance, but I've been running this setup for years and it "just works" for me. I understand how it works, I know how to back it up (and, more importantly restore from that backup!)

If there's another open-source, self-hosted project that has WebDAV, CalDAV, and CardDAV all in one package, then I might consider switching, but for now Nextcloud is "good enough" for me.