I have to disagree. While the show did change showrunners and gears to a more action-oriented production, it didn't wildly change the premise. While they were trying to regroup at the beginning of season 2, I felt they regained their sense of purpose by the middle of the season and the back half was really enjoyable.
No, it didn't change the broad premise, but it changed the approach, the voice, the characters, the style, the intelligence. The new showrunners may have been trying to tell the same rough type of story, but the emphasis and substance were completely different. Richard C. Okie was telling a challenging, sophisticated story about truly alien beings with alien agendas that could be both benevolent and dangerous due to their profoundly different outlook and priorities, and the quest of William Boone to defend humanity both by countering the Taelon's dangerous actions and trying to help Da'an gain a better understanding of humanity. Under Okie's successors, all of that changed. The Taelons were reduced to more humanlike characters, with Da'an falling into a "good guy" role while Zo'or increasingly became an overt and un-nuanced "bad guy." The idea of using the premise as a vehicle for commenting on the human condition was lost, and the premise became merely a vehicle for action. All the nuance and complexity were lost. All the characters were simplified, retconned, or replaced. I don't consider that the same show at all.