You don't really own any of your cloud data, even if it feels like it. If you want to own your data then it needs to reside on private computers in private spaces - though that does not preclude you from sharing but you lose control of what you share.
This is a key reason for why I started Helm - thehelm.com. There's a lot of talk here about the hassle of self-hosting and while many HN folks are perfectly capable of running their own servers/services, it can be very time consuming. We take away the hassle and provide the benefits of self-hosting at home.
I don't self-host everything, for me it's enough if I can take out all my data. I have all my cloud hosted things mirror via rclone to local storage. So I'll gladly use git, IMAP, CalDav, CardDAV as a service but I'll have my local hot mirror and cold backups ready any time. Tools are readily available:
* git is git and clones
* IMAP gets pulled via mbsync
* CalDAV, CardDAV get pulled via akonadi and exported to flat files from there
* Remote SSH/SFTP accessible storage gets pulled using rsync
* Other remotes get pulled using rclone
https://en.wikipedia.org/wiki/Third-party_doctrine
You don't really own any of your cloud data, even if it feels like it. If you want to own your data then it needs to reside on private computers in private spaces - though that does not preclude you from sharing but you lose control of what you share.