The range of pro/power users happy with the iPad right now looks awfully small to me.
[0] https://www.wacom.com/en-us/products/pen-computers/wacom-mob...
people who want to use their iPad primarily for writing will want a keyboard + touchpad
people who want to use their iPad primarily for drawing probably won't want a keyboard or touchpad
I don't know why someone would choose an iPad for drawing rather than a MobileStudio Pro, you'd have to ask someone who draws on an iPad.
Personally, my iPad is purely a video and reading device, so I'm not the target audience for either. I'm guessing you aren't either.
On how much it's filling them correctly, outside of people's feelings we only have a few indicators; I'd say this few years' steadily declining sales could be the best summary ?
I'm totally with you: the iPad looks like a competent device from every angle. That's why it's so sad it's only the looks and you have to bend over backwards for basic stuff like selecting a text from a web page or an app straight touching the screen.
For comparison, as much as Windows is ugly and inelegant, there's no basic action on a Surface Pro that requires an attached touch pad.