yeah, the background art looks like art made for a game, not for an animation. it even has a visible palette! and it tiles, and is locked to a flat horizon.
Also the speedlines? on the ground dont work, it looks odd to jump to it from the detailed ground and back again, and when they're shown together in the side run, they're different colors, and the line at the top of the speedline ground is jarring.
check out
https://www.reddit.com/r/BackgroundArt/top/?sort=top&t=all , there's some great examples of backgrounds made in a way that does not detract from a character moving in front of it.