It's funny because I agree that the story feels inconsequential, but in terms of the main plot, way more happens in S3 than S2 and S1. Let's compare:
S1: Ryo's dad is murdered, he finds out about his secret trip to China, then finds the Phoenix Mirror and goes to China.
S2: Ryo finds Lishao Tao and Yuanda Zhu, learns a bit about the mirrors, and meets Shenhua.
S3: Ryo learns the origins of the mirrors, gives the Phoenix Mirror away, and fights Lan Di!
If S3 really leaned into how momentous those events are, it absolutely could have felt like Empire Strikes Back. The biggest problem is that S3 buries the lead and most important things happen in rapid succession at the very end after almost no build up, so they barely register. Why don't you think S3 would have gotten there?