I agree with some of what you are saying, I also expected the integrated graphics to be stronger already.
But, I think the only way to achieve dramatic improvements are to make them custom like in the consoles or a separate socket that allows the die size to be larger. They currently have to keep the die sizes the same as the normal processors, which I think limits the available space.
The xbox one for example had a much larger die or chip size, so it had like the GPU chip of a HD 7790 (or something like that) and then 8 energy efficient CPU cores built around that graphics chip. As you can see here I think this is larger than standard size:
That small block in the middle is likely the HD 7790 (if I remember correctly) GPU chip itself, and on integrated graphics I bet it is 1/3rd of that size.