Why are they outraged about this? So many dramas have historical inaccuracies but they don't get cancelled when…
Well, because recently there are some controversies regarding hanbok and kimchi which were said to be appropriated by some Chinese internet stars. Some Koreans are angered with these actions, while some of the Chinese kind of viewed Korean cultural symbols are rooted from Chinese culture. The drama just came out when the tension is still high and they're not keen with anything Chinese in a middle of sageuk (despite the situation of the scene - near Chinese border). And when two revered Joseon kings are portrayed a bit inappropriately, it just add more fuel to the situation.
Horse Doctor is good if you compare it to other long dramas, it’s long but keeps you interested along the way. But still I didn’t rate it that high haha
2 
To be honest it made me even want to watch it more
I watched Indonesian sub from here (raw available, in case you still want to watch eps 9.-10): https://bagikuy.com/heaven-gokuraku-restaurant/
Part 1: https://www.xile.tv/vodplay/239103-1-2.html
Part 2: https://www.xile.tv/vodplay/239103-1-3.html