Hi there, thanks for the nice article!
However I think group has its place to stay.
It allows more intuitive control over the elements, for example, you don't have to worry about dragging an element out of the frame it belongs to. Also it is a pain in the ass when there's frames in frames in frames.
Besides, personally I think the resizing issue you mentioned is over-rated because we would have dedicated frames/variations for different width to demonstrate the behavior.
I agree that when there's extra time or the elements are going to be massively reused, making everything in frame is best practice, I do that as well. But groups are more handy in the process and not using it altogether may create more problem than it solves.