This is my own personal opinion. I am not an anti-fan. For those who want the ratings to be higher, you need rate every episode. It's not an anti fan problem. The issue is that people don't rate.

I am a ZLS's fan as far as acting. The acting is amazing, and she has grown a lot since her last drama. However, the script is not as entertaining.
I think the script needs to be less complicated, more leads time together, more interesting content, more humor, etc.

Production: 10 Amazing special effects, very high end visuals
Acting: 10
Script: 7 borderline boring up to 6
Director: 6 (Just look at how LLTG is directed. That drama is 10+)
Emotional investment in the character: 2 (this is a script/directing problem)
Chemistry: I am a fan of this couple from the Long Ballad. The chemistry there is amazing. Some how I don't feel it here yet. It's the director and script I think.

However, I am going to wait to see how the story develops after 10 and will change the rating as required.

THE PLOT
Conflict - pearl trading with a revenge/ hidden identities twist, and government investigation. Amidst all this, a young girl develops her character, discovers her true identity, and becomes a jewelry business woman.

eps 1-6 : sets up the backdrop - I think this could be done in 1-2 episodes. But they dragged on. While ZLS acts well and looks amazing as a pearl diver, I think if the script is not entertaining/funny, it's going to be a drag.
If you watch, LLTG, the director is good there and the rating shows it: It's boring family fighting, but he made it fun and entertaining to watch. It's a piece of art.
In contrast, The Pearl Girl, amazing production and special effects, is not skillful in presenting the material in an entertaining and artful way. It's more like Hollywood Little Mermaid with too much other things and graphical violence going on --- Like Korean drama!

eps 7-8: It's beginning to get interesting because she is finally involved in something more meaningful: negotiating trades and dealing with business. She also made a femal friend to help her out instead of struggling by herself. You can see where the plot is heading: Zhang Jin Ran told the girls that in Chang-an, there are shops run by females.

eps 9-10: predictable the way it's filmed. He tricked everyone to believe that he killed the accountant. I still don't feel good about the script. Very mediocre. I don't think it will do well beyond the 8.2-4 range. There are a few story holes - like why she is so strong and can take on the bad guys in fighting. I think the director of this drama is not a good one.