MMH5.5 - Heroes of Might and Magic 5.5

Why should all cities be production-focused and aim for a full buyout?
And why should all tiers be built and purchased immediately, even in production-focused cities?
This can only be explained by a desire to extract the absolute maximum from all cities, but then the question arises: why should this be easy or even achievable?

Heroes 5 simply spoiled the players – on all maps, there are a lot of mines, and the income from the city is enough for a full buyout, and the building process is also prolonged due to city levels, which practically eliminated early rushes with small armies. That's why people start considering the lack of mines as a bug that the mod authors must fix, otherwise, it's impossible to play.