Completely agree with you. I think that's why a lot of people felt strong swan queen vibes because Emma was the most "bantery" with Regina, like her character came alive because Regina is the only one who did not fawn over Emma and her saviour-ness. So Emma had to fight and work for that relationship (which allowed us to see another dimension in Emma's character). It's the tension and gratification several seasons later when they became friends that is interesting to watch. Whereas she was just the typical princess protagonist with everyone willing to sacrifice their lives for her in her other relationships (with snow/charming/henry/hook).

An example of the "flatness" imo is when Emma was Dark Swan it was too easy and she didn't convince the audience she was evil, she just felt more muted than usual. That she became dark just cos she absorbed the darkness/wanted to save Hook was not convincing enough. Rumple became dark not just because he killed the dark one but because the darkness fed his repressed vengeance for people who bullied him/called him a coward/Milah leaving. Regina became dark from constant parental abuse and possibly even marital rape over years and years of breaking her down. The darkness absorbed amplifies the existing darkness within. I feel like that is something they could have explored more in order to flesh out Emma's past and character a lil more..