The economies of the Sengoku Daimyo and Japan are simply too strong, and both civilizations have very powerful military units.
Sengoku Daimyo gets extra food income from Yatai in the early game, and Matsuri can reach full efficiency very early on. For a long period of time, Daimyo’s overall resource income is better than that of many civilizations that lack strong economic bonuses. If a Sake Brewery is placed nearby, Daimyo also gains a very solid amount of additional gold income.
Japan is even more extreme. As early as Age II, Japan gets free farms. In Age III, Yorishiro provide production speed bonuses and “free” virtual resources (and if it is Byōdō-in, it generates a massive amount of virtual gold). On top of that, the mounted samurai units of both civilizations are extremely overpowered. Daimyo’s mounted samurai can reach a terrifying 1.06-second attack speed in Age IV, while Japan’s mounted samurai have deflection armour and up to 38 attack, which is crazy.
So, with such strong economies, Japan and Sengoku Daimyo can completely crush many other civilizations from Age III to early Age IV. I believe this is unacceptable. Civilizations with very strong military power should not also have such excellent economies.
Taking Macedonians as an example: aside from silver income, they have almost no meaningful economic bonuses at all (the radius of the Grand Winery is laughably small). Because their economy is genuinely weak, players can accept units like Riddari and Varangian Guards being relatively strong — the tradeoff makes sense.
By contrast, civilizations with strong economies should logically have weaker military power. China is a good reference here: despite having a very strong economy, most of its military units are generic and receive little to no direct combat bonuses.
Japan and Sengoku Daimyo must be nerfed either on the economic side or on the military side. If both remain this strong, they are simply far too overpowered.