I have a Galaxy S5, and have encountered the same types of problems with the baked-into-the-OS Google services. I have rooted the phone, installed app-ops (useless Google window dressing), and then xposed framework and xprivacy. The level of intrusion and data capture is simply stunning.
The first thing that usually blows people mind is when they visit Google GPS location history page at https://maps.google.com/locati... - even though they weren't aware of it, every move they've made for months has been tracked down to the minute by Google. You can "turn location history off" on that web page, but the GPS is so baked into the OS that this cute web page checkbox is almost guaranteed not stop the continuous GPS gathering. In fact, after blocking location access by GPS, you get a stern warning "enable location services for gps", and the "do not ask again" is greyed out if you do not allow it, you will get nagged regularly.
Your phone is essentially rooted. If it can ring remotely, be located via GPS and be disabled by "find a phone" features, it is not you that has root on the OS. It is the company that can employ that at any time.
The Google intrusion is multifaceted once you start digging in, dozens of different components of the OS that make contact with external servers without documentation. Spending massive time disabling their access to your personal data one by one will usually result in a borked phone. One of those back doors is going to get your data even if you think you turned everything off.
Then we have the Samsung apps that are in full intrusion mode. The health app? Wants your contacts and location. The keyboard software? Wants your contacts and location.
It is of course impossible to use these devices without your entire contact list, phone and text engagement, password list, etc, being scarfed up and sent to the cloud. Any single OS library that has network access can act as a gateway to other components that look like they are otherwise behaving when they access your clipboard, screen, etc.
The biggest problem is not that every aspect of your life is tied together by a corporation, who has recordings of your voice, keystrokes of everything you've typed, pictures of you that are run through facial recognition, etc. It's that this is all going over the wire to a corporation that is too big for one government to reign in. A corporation that has had their internal communications tapped by the NSA. A corporation that "plays ball" with law enforcement by giving them their own handy web portal to data. And of course is all behind one password that can be hacked and cracked on by the entire world of hackers from lawless nation states. Soon coming to a Windows 10 computer near you.