I personally like these types of plots a lot. They may be about the same type of couple but the plots are in no way (Most of the time) similar and the stories always bring something new that we haven't seen before, different romance, different struggles, different side characters, different back stories, etc. Also, most historical dramas (Not wuxia or fantasy)relate to something that happened in the past (Not often but mostly), by making these types of plots it is more realistic. I also wanted to add that there has been a few bans in the past and present on Historical dramas, this is because some people view certain plots as disrespectful to their ancestors (Don't quote me on this though because it is just what I have heard, i am not Chinese and I don't know this in detail). But despite there being a lot of dramas about Emperors/Princess and Empresses/Consorts/Concubines/Princesses/etc, there are a lot that don't involve these types of plots.
Examples are:
Love and Destiny
Love Better Than Immortality
Under the Power
General and I
The Legends
I've Fallen For You
Ancient Detective
Chef Hua
In conclusion, no. I personally don't get bored by these types of couples in Historical dramas because each plot brings something completely new to watch :)
