Except for the exceptions. Like mine. I don't need the functionality you're describing.
Just my personal story: I've been using mask shapes in AE since they were invented. The function has been easy for me and they perform exactly as I expect them to, even though today's AE is a million times more complicated than Ye Olde CoSA. I have Illustrator artists in my shop who watch me work and they say they don't understand how AE's mask works or how I can possibly use the tools. Can't confirm or deny. I don't use Illustrator. I don't really care that it might work differently than AE's vector drawing tools.
Besides, I don't trust any of my coworkers' opinions about these things; they're not video people. They're, you know, graphics people.
And now we live in a world with Motion Graphics.
Done, largely by default, within AE, an app that's inherently designed for compositing video, as you rightly point out.
The masks and paths of AE never considered the intrinsic nature of motion graphics, so much like Flash before it, much motion graphics creativity is restricted by the path tools of AE.
There's an opportunity there, somewhere. Apple's Motion has dropped the ball, some of the worst "preview" non-functionality known to man. Almost unworkable.
At this point in time, the best place to do 2D motion graphics is within a 3D animation app like Maya, Max or C4D.
Just one more thing.
Thanks for the admission that Masks and Paths aren't all that we might assume they would be in 2014.
That's a bit of a breakthrough and a relief. I thought I was searching for functionality that I couldn't find, that must be there... for the longest time.
It seems Adobe has an issue with admitting to the (many) limitations of their software.