Yona and co can't brute force anything. They need powerful allies to knock down Suwoon. And the one who supporting them to fight against the current king and the sky tribe is not openly enough and powerful, like Lady Lily, Taejun, etc
I totally agree, BUT - Yona got to the where she is not by being pushed around, she worked and fought hard to be there! so WHY is she acting so obediently now?! She can decided how and what she wants to do, She is the true king and the ruler of dragons!
It was her who should have sat at the kings sit!
I believe she acts obediently for the safety of her dragons and to prevent chaos within the kingdom.
The citizen of Kouka now knows that the legend is true and Yona is the direct descendant of King Hiryuu. They basically worship her and the dragons now (see how the fire tribe soldier treats them) But they didn't know the truth.
If they know the reason behind King Il's death is Suwoon, Kouka would be divided into 2. One is the Sky Tribe with the citizen who believes in Suwoon as the current King. Two is the citizen who believes in Yona as well as a few nobles like Lily and Taejun
Why are you allowing that?! the princess, this is too much. It's like she is back to the days where she was weak and hopeless, this is FRUSTRATING!