It's terrible, the whole point of the movie was that Spirit could not be tamed. He was meant to always be free. Sure he made a human friend in the movie, but it even took him until the end of the movie to ride him, and even then the guy let him go saying, "He was never meant to be ridden, but to be free."
The whole point of Spirit as a character (even if he if is a horse) was that he could not be broken, he was strong. The whole moral of the movie was to always be yourself and stand your ground, to never let anyone break you. This show just completely rewrote it. It's really really bad.