ha ha, I know right?
Yes, Jack Kirby is amazing. I love his comics, and I love the frenetic, idea-driven style of comic he created and eventually perfected. What I don't love is one specific outgrowth of his influence. Before Kirby, the Platonic ideals of action comics art were Hal Foster and Alex Raymond, both essentially realist figure artists. A massive part of Kirby's genius was his arrival at a way of cartooning the human figure in motion, using foreshortening, large areas of spotted black, and his own titanic style to create a convincing simulation of reality that owed precious little to realist anatomy. That's not to say Kirby didn't understand realist values -- his early comics testify to at least as good an eye for the figure as the average Golden Age artist, and he's on record about the lessons he learned from both Foster and Raymond.
But the artists who inherited Kirby's sphere of greatest influence -- that is, superhero comics -- had a new ideal to work from. Kirby's followers are almost uniformly victims of his success. No action artist since has assembled a cartooned style that presents dynamic figure drawings as successfully, and the Foster/Raymond fallback of inserting realism where dynamism falls short has warped into something that simply doesn't work. Rather than wedding realist, workable anatomy to Kirbyist gesture, composition, and dynamism, the common solution seems to be a combination of Kirby anatomical distortion (the over-muscled men and blow-up women stereotypical of superhero comics) to more realist, observation framing.
The tiny head, lack of neck, thick wrists, squat posture, and tree trunk legs work in Kirby's version because it's a sharply foreshortened action shot -- not only are some body parts hurtling toward the camera and some thrown back, the anatomy is less likely to be noticeable as non-realist (which it is) because we're paying attention to the pose. And the impact of the picture is actually enhanced by seeing the figure thrown out of proportion -- it's like hearing a musical dischord, it puts you right on the edge of your seat.
The modern version (example above by Olivier Coipel, who I actually think is better than most and don't intend to call out specifically) pulls from all Kirby's anatomical distortions and none of his dynamism. A completely static pose is only made more problematic by the obvious lack of attention to realist anatomy. Though Kirby's version is much more broadly cartooned, it's a far more convincing piece of artwork because it's fully aware of what it's doing. It has an internal logic that the work done in his shadow lacks, with its strange combination of observational framing and dynamic figure. Kirby's characters always moved, and as such they were designed for constant motion. Freeze them in place and they fall apart, as today's superhero art is showing on a weekly basis.
My advice to the modern action artist: go look at some Hal Foster comics before you get to Kirby. We can't all be visionaries, you know.