I think that’s kind of what they meant. I’ve also selfhosted Nextcloud for years, but I only use file sync and calendar/contacts.
Lately I’ve been feeling that Nextcloud is too big and clunky for just that. Like it’s something I’d love to setup at work or for an org, but that it “feels” to heavy for home use these days.
I need to check out Radicale, I think.
KDE Plasma used to have one like the one on the right a few years ago, and I was so glad when they ditched it. I strongly prefer the organized look of the left one. I always had a hard time finding anything in the old KDE/MacOS settings.