This might just be rumor but I've heard the Eight Princes DLC was a huge misstep for CA with the Chinese market. I'm not an expert of Chinese history but the gist is that it happened 100 years after the Three Kingdoms and apparently in modern China is not a proud era in their history because it more or less ended with Northern China descending into chaotic rebellions and within 4 years of the war's conclusion the entire region was being ruled by foreign barbarians (Steppe tribes I assume?). So apparently not a lot of enthusiasm for another reminder of the time China couldn't keep their shit together and became subjected to foreign rule, a sore subject for them now.
I'm not sure but maybe because of that, the first major DLC was more or less a flop in sales numbers, the steam charts always showed how few people were actually playing 3K when DLCs came out, it wasn't impressive. After that, I think they couldn't decide between pleasing the folks who wanted more fantastical stuff (Warhammer crowd?), and the hardcore history crowd, tried to split the difference with the Nanman DLC which ended up completely ruining the game balance, according to some. I honestly only played one campaign when the game released and never touched it again.
Overall the only reason CA would abandon this hard is if the sales were extremely bad, and I could absolutely see why they'd be bad seeing as how they sorta pissed how their Chinese market right away, and the western audience doesn't care for Three Kingdoms nearly as much as they like Warhammer fantasy. I hope this taught CA a lesson but I doubt it.