I don’t think the poor ratings necessarily have to do with whitewashing. Or at least not just that. I mean, Empress Ki had good ratings and it’s hard to get more ‘whitewashing the villains’ than that drama - all three of the leads got a hell of a make-over from reality!
I wonder if the lack of a hot (in terms of market power) star is partially responsible. I mean, Lee Je Hoon is a good actor but he’s not a Sageuk It Guy the way, e.g., Jang Hyuk was in Chuno or Tree (or Lee Seo Jin used to be). To compare the cast to another ahistorical sageuk, Empress Ki did have Ha Ji Won as the protagonist, and her star power alone is probably bigger than that of the entire cast of SD combined. I do think any drama starring the amazing Han Suk Kyu should have all the ratings in the world, regardless of historical accuracy or even merit. (I am only half-kidding).
Also, now you reminded me of the mess that was JOJ. Whoever thought it was a good idea to green light that drama was insane. Not only is it contrary to accepted history, it was also crazily cast, was fusion in a weird, not good, way, and went absolutely nowhere. And the history thing - what were they thinking? It’s not like Empress Ki, where the drama covers a murky, less-popular period or Queen Seon Deok, where in making Bidam the very ahistorical love interest, they made an army of obsessed fans super happy, or even Secret Door, where it’s just a more extreme version of a narrative that has popped up before - dramas often tend to make Sado more of a tragic/complicated figure than just a violent lunatic who probably needed to be put down (even if not in the horrible fashion his father did it - that method of death freaks me out beyond anything). No, JOJ took one of the most known in popular consciousness historical narratives and turned it on its head, and not even in a particularly clever, post-modern way. I mean, if you want to make a period love story, by all means do so, just not with JOJ! There are plenty of obscure historical figures to pick from, or go the Moon/Sun route and create fictional royals even. JOJ loooooove isn’t going to fly.
OK, now I completely derailed from the topic. And have a mad passion to rewatch a Lee Seo Jin sageuk. Heh.
One last comment re: Secret Door husband/wife thing - if the show portrays him as this wonderful idealist, then the ship works even less because even a fairly ahistorical production is not going to deny that everyone knows that his widow wrote memoirs portraying him as a psycho. They’d had to explain why a widow of a sweet dude did that and whatever the reason, it can’t be because they were in loooooove :)