It sounds to me like you're mostly in agreement: situations in which you want full manual (including ISO) are rare. Most of the time what you care about is either the aperture (setting ISO and shutter speed to get the correct exposure) or the speed (setting aperture and ISO to get the correct exposure).

For non-pros like myself, it's unfortunately not common to shoot with a camera that has good auto-ISO: basically anything above ISO 800 is going to be unusable, and ideally you want ISO 100 or 200 if your lighting situation can allow for it.

So most of the time I find myself in semi-manual modes: where I lock the ISO to a setting that's ideal for the light I have, use auto-focus (unless it's failing to lock on the correct target), and set either the aperture or shutter speed to what I want. The camera then adjusts the other factor appropriately, but I still find myself using Canon's quick adjustment exposure compensation tool almost constantly because my Canon blows out highlights pretty badly a lot of the time.

For a pro I imagine the situation is usually reversed: set both shutter speed and aperture how you want them, and trust your camera to be good enough with the auto-ISO. It sounds to me like GP was basically right: in a non-controlled setting, full manual mode is pretty rare.