I won't speak for GM but I agree with his assessment on the character design in Eternal being a nod to the source material.
People say they look cartoonish which I understand however I think it's because of the colors they used which again is VERY reminiscent of the original games.
The soldiers for example with the red eyes are a throwback to the original games. I wish some would also have the green hair but that's a meaningless nit-pick on my part, to be fair.
DooM 2016's models seem to be going for a more gritty realistic look. While Eternal's actual designs still have a realism about the models (NOT comparing them to 2016) it's the colors that I feel some people say it looks cartoonish.
I'll only speak for myself here when I say that essentially everything about this game aesthetically is a throwback to the originals using current tech (ID Tech 7). Even other things like the grunts are a nod to the foundations.
To answer the topic, the simplicity of DooM 2016 is more noticable now after Eternal. I say that in a positive way, mind you and that would be my answer.
Currently Playing: DooM: Eternal (1X), Diablo 3 (1X), NBA 2K19 (1X)