I think there were many points in the show where they could have changed things for the better, and tried to make it less confusing all around, I don't think the shows it self is bad, but they could have expanded the possibilities of the shows to make it better, and use the side characters much more then they did or have. 

It's not a bad show for Korean standards but I have seen better.When I say Korean standards don't get me wrong,I like kdramas but mostly for the visuals and the warm feeling,I can hardly call them masterpieces.The are a bit immature and shallow for me next to some european shows ,unlike their movies that can be very good.So I don't really understand how people can complain so much about the plot and character developement when dramas like this focus too much on good looking leads,pretty clothes,product placement and nice stuff anyway.

Imo, this question should be asked at the end of the drama and actually can be read in review section