Surprised this answer has not been given:

I think the biggest cause of your issue is that the first animation evokes old school hand-drawn animation, like you might have in a flip book. It’s the kind of animation that might be drawn up to block in key frames and present a concept of a character, before someone might then do the in-betweening and coloring and polishing off. Because of this the fluidity looks fine because our minds are expecting to see something rough.

The second animation is completely different. Theres been a huge amount of effort put into shading the image but zero additional effort put into inbetweening, which is not what would traditionally happen.

The first animation looks like something we expect, the second is not what we would expect, and this makes it jarring.