Android has been a fraud for a long time now. Let's not pretend that the "open-source" mobile OS that was supposed to free us all from vendor and telco tyranny ever approached that promise.
Did they even really try?
As far as iCloud "alternatives" go... Android doesn't offer ANY legitimate syncing infrastructure to compete with iCloud, open or not.
The point is to sync application data between native apps running on different (and even different kinds of) devices. PIM-style data (calendar, contacts, notes, bookmarks, and so forth) probably comes first for most people. Apple has also added useful stuff like Wi-Fi passwords and E-mail account configurations.
And then developers can create their own entries in the iCloud data store for their own apps. This is hugely useful.
I'm not aware of any similar facility that comes with Android, but I'd be happy to hear about it if there is.
Did they even really try?
As far as iCloud "alternatives" go... Android doesn't offer ANY legitimate syncing infrastructure to compete with iCloud, open or not.