If you're an Apple user, turn on Advanced Data Protection
If you're an Apple user, you should turn on Advanced Data Protection. It's an optional security feature which encrypts most of your data in iCloud, including your backups, photos, notes, and your Messages in iCloud encryption key. All very personal things that you would assume to be encrypted, but which are not and are therefore accessible from Apple servers.
There is an additional layer of responsibility put on you if you do this: you must safely store your recovery key because Apple won't be able to help you recover your account data.
Unfortunately, Apple hampers iCloud Drive so I don't consider it a replacement for something like Google Drive or OneDrive. But for some of this other personal data, Advanced Data Protection makes iCloud worth it.