Looking back at the end of the historical drama golden age, works set in the Three Kingdoms/Goryeo eras failed miserably...

I just thought of this while looking at the following:
The golden age of historical dramas lasted roughly 10 years, from '99's Heo Jun to '09's Queen Seondeok.
During this period, historical dramas were practically a guaranteed hit,
but a strange trend started emerging after the mid-2000s.
While works set in the Joseon Dynasty still maintain a high success rate,
works set in the preceding Goryeo and Three Kingdoms periods have failed miserably.
It started with Shin Don, and then Yeon Gaesomun...
Both of these became laughingstocks on the internet...
After that, Empress Cheonchu wasn't just a laughingstock, she was heavily criticized,
and what came after was that famous Three Kingdoms trilogy....
King Geunchogo - Gwanggaeto the Great - Dream of the Great King....
In effect, this trilogy completely ended the golden age of historical dramas.
That is why historical dramas released from the mid-2010s onwards
hardly even look at the Goryeo or Three Kingdoms periods;
whether it's authentic or fusion historical drama, they are only focusing on the Joseon Dynasty... (including the transition from late Goryeo to early Joseon...)
The only exception seems to be Korea-Khitan War? Hmm...