The plot of the movie "Assassination" (Please provide spoilers)

Doubts regarding the assassination of First Lady Yuk Young-soo have been a recurring topic since the 90s, so
I didn't particularly feel the need to watch it.
Is this movie controversial because its main plot suggests that the government (the Blue House) was involved in the assassination of First Lady Yuk Young-soo?
It's such a familiar topic that it feels more like a conspiracy theory, so why is it suddenly becoming an issue?!