I haven't watched either Borgia series, but I enjoyed the article because it articulated something I've long come to realise: historical nitpickery frequently misses the point. Historical fiction doesn't need to be a picture perfect reflection of the past, because often that would lead to a lot of time-wasting due to the need to translate every tiny detail to make it comprehensible to modern viewers. It's enough if the overall attitudes and motivations for the characters make sense for someone of that historical and cultural time period.

Fiddler on the Roof sounds like it would be a good Yuletide fandom, and I bet you'll find people willing to write it. I don't have any personal experience with kdramas and Yuletide, but I'm peripherally aware that Crash Landing On You was pretty popular in Dreamwidth circles this year, so maybe you'll have more luck this time.