*One of the reason is that Ming simply had too many population. Despite its food production per area unit was a few times better than Europe, it still struggled to feed all that many people. So most of manpower had to stick to farmland, and there weren't many surplus left for tax. And every and any slight drought or flood might tip the balance to hunger and starvation. Peasant revolts were doomed to happen, a lot. The situation was only relieved by introducing of new-world crops like maize, potato, sweet potato in 17th ~ 18th century.
In game's term, it should be represented as "Burden by Population" province modifier that gives penalties to tax, manpower, product efficiency, and possibly trade power, and DHE to remove that modifier when circumstances are right (for example, when a new world colonizer also colonize in a nearby region like Phillipines or Taiwan, or the controller (Ming/Qing/whoever) itself somehow colonize the new world).