Here’s how I view it:
You’re not allowed to bring weapons onto an airplane obviously, so they have to check your bags first. But wait, these are my personal belongings! I mean, I know I don’t have any weapons, but can’t they just trust me? Why am I treated like a criminal before I’ve done anything wrong? Can’t they just check my bags once I’m on the plane? Once my bag is on the plane, they can go through it all they want, just not before hand.
In this example, the plane is iCloud and the stuff in your bag is what you’ve chosen to put into it.
Turning off iCloud Photos is like canceling your trip. Nothing is checked because you’re not at the airport getting on a plane.
Bottom line, don’t collect CP and nobody will ever view your photos. 100% privacy