Moon Geun Young actually did an amazing performance, and what you're saying prove it. :)
Because the whole aim of her character was to "disappear" in front of the others characters. She couldn't distract the viewer attention from the story.
A cut from "dramabeans.com"
"PD Lee had a lot of praise for all of his cast, but the majority had to go to Moon Geun-young, who was technically the lead, and Shin Eun-kyung, who was at the center of the mystery.
Truth be told, Moon Geun-young’s character never felt like a lead, or a compelling character—she was the least interesting character of the bunch, with the more complex stories and emotions being given to the supporting cast. That’s been indicated by the press and fans, and the flipside to having a cast where everyone felt like a leading character is that your actual leading character tends to recede.
But when you look at the drama as a whole, that seems to have been a calculated, deliberate decision on the part of the producers. PD Lee said that he was extra grateful to Moon Geun-young—not for stepping it up as the lead, but for knowing to hold back and not insist on doing the most dramatic work. He explained that in other dramas, the lead is the one getting the most attention, but he wanted So-yoon to be weak, and she understood that.
He said, “So-yoon isn’t magical or particularly special, she’s an ordinary person. She’s just tenacious about finding the truth. Once, I mentioned Silence of the Lambs to Moon Geun-young, that if Jodie Foster’s character Clarice Starling were too strong, there would be no suspense. The suspense was able to exist because a fearful and weak character met a serial killer and faced off against the truth. I told her that So-yoon in this drama is like Clarice Starling. When I said that, Moon Geun-young’s eyes sparkled.”
“I was surprised when Moon Geun-young agreed to take the role,” PD Lee also said. “But she said she likes these kinds of things without lovelines. She found it refreshing that it wasn’t a Cinderella story, and to see things from the perspective of an observer.” "
Because the whole aim of her character was to "disappear" in front of the others characters. She couldn't distract the viewer attention from the story.
A cut from "dramabeans.com"
"PD Lee had a lot of praise for all of his cast, but the majority had to go to Moon Geun-young, who was technically the lead, and Shin Eun-kyung, who was at the center of the mystery.
Truth be told, Moon Geun-young’s character never felt like a lead, or a compelling character—she was the least interesting character of the bunch, with the more complex stories and emotions being given to the supporting cast. That’s been indicated by the press and fans, and the flipside to having a cast where everyone felt like a leading character is that your actual leading character tends to recede.
But when you look at the drama as a whole, that seems to have been a calculated, deliberate decision on the part of the producers. PD Lee said that he was extra grateful to Moon Geun-young—not for stepping it up as the lead, but for knowing to hold back and not insist on doing the most dramatic work. He explained that in other dramas, the lead is the one getting the most attention, but he wanted So-yoon to be weak, and she understood that.
He said, “So-yoon isn’t magical or particularly special, she’s an ordinary person. She’s just tenacious about finding the truth. Once, I mentioned Silence of the Lambs to Moon Geun-young, that if Jodie Foster’s character Clarice Starling were too strong, there would be no suspense. The suspense was able to exist because a fearful and weak character met a serial killer and faced off against the truth. I told her that So-yoon in this drama is like Clarice Starling. When I said that, Moon Geun-young’s eyes sparkled.”
“I was surprised when Moon Geun-young agreed to take the role,” PD Lee also said. “But she said she likes these kinds of things without lovelines. She found it refreshing that it wasn’t a Cinderella story, and to see things from the perspective of an observer.” "