Q: How can I come out of icloud drive and revert to icloud.co?

iCloud Drive FAQ - Apple Support

You cannot revert to "Documents in the Cloud", you can just stop using iCloud Drive, once your iCloud account has been upgraded to iCloud Drive. There is no way back.

From:   iCloud Drive FAQ - Apple Support

After I upgrade to iCloud Drive, can I downgrade and go back to using Documents in the Cloud?

No, after you upgrade to iCloud Drive, you can't go back to using Documents in the Cloud. You can turn off iCloud Drive in iOS 8 by going to Settings > iCloud > iCloud Drive. You can turn off iCloud Drive on your Mac by going to Apple menu > System Preferences > iCloud and deselecting iCloud Drive. If you turn off iCloud Drive, your documents and data will no longer be kept up to date across all of your devices.

Also see:  iCloud: About using iWork for iOS and iCloud