GPS button?

You may work in IT but apparently you are not very good at doing research. It isn't exactly a state secret that Apple has the corporate attitude of they know better and they do not allow a much customization. As to what you are wanting to do it isn't referred to as GPS in iOS it is location services. Turn that off.

But if you had a phone from a manufacturer that was using a significant amount of battery leaving GPS on then you had a defective phone and should have gotten it repaired.

But I agree with lkrupp, your question clearly shows you are not happy in the Apple ecosystem. The good news is iPhones have better resale value than other smartphones so sell yours and get another Android model. And if GPS is using a lot of battery get the phone serviced. Keep in mind too that most people with iPhones used Find My which helps with locating the iPhone if you lose it and turns on Activation Lock in case of theft. Turning off GPS defeats this.

Return your Apple gear and move on. All you’ll do is wind up complaining about how superior Android is and how iOS has no basic functionality. You’ve already stated as much.