I think I know what bothers me about the artwork.
It kinda feels like someone took ball joint models, set them up in poses and photgraphed them and traced over those to create the body of each character. Probably 3D models being used as a base, if I had to guess.
The hands always looks stiff in the same couple positions where the fingers seem locked in place, and there's a weird rigidness to the body itself, even in very dynamic, in-motion poses.
Almost like I'm looking at jrpg character graphics on the ps2 or something. Technically in 3D, but the modeling tech leaves the character more like a semi-flexible doll but with none of the life-like range of movement you'd expect.
And the poses in each frame look like they were staged for a studio shot, rather than as though a photo capture of a point in time in the middle of a dynamic ongoing fight.
Just very stiff and posed overall.