This is very impressive. It's also a game designed for a particular audience which very much does not include me, and I will not fault the game for that. I can barely handle the tactical complexity of a Fire Emblem game and a 4x strategy game is at least 2 more x's than I can handle. The game seems feature complete and I can't really critique it other than that it's an overwhelming amount of information right at the start, but high complexity is probably a good thing for the target audience. If you wanted to improve onboarding, maybe you could include a short tutorial campaign on a smaller map with only 2-3 characters instead of the full scale campaign? Maybe it could be something from the prologue events, like the death of warlord Dong Zhuo or something.

If you want to expand the game further, I'd recommend unifying the artstyle. You've got at least 5 different styles for character portraits, combat units, cutscene backgrounds, battle maps, the campaign map, the faction map in the opening cutscene, and the upgrade icons. If you can find a way to make all of these elements fit together smoothly, it would make the game look a lot more polished. As it stands, it looks as good as it needs to.