topsy the collapse of the Chinese economy by the 19th century was only marginally the result of western imperialism, and the opium imported by the west only met a small proportion of the demand for opium, the top end of the market. 90% was grown in China (see Frank Dikotter, Lars Laaman Narcotic culture, a history of drugs in China - good book, upends a lot of existing academic assumptions, Julia Lovells book on the Opium wars is good too)
Pre 1800, prosperity was in fact effectively based on a free trade block. China did not absorb states like Tibet, instead they became tributary states whose rulers kowtowed to the Emperor but more importantly they became part of a vast free trade area. However the economy became increasingly dependent on silver which, originating in the Spanish mines of South America, the Europeans were using to pay for commodities like tea. It became the basis for the coinage and taxes were paid in it. As the price of silver was twice in China what it was elsewhere in the world more silver was mined and flowed to the UK economy which flooded the Chinese economy causing deflation and an economic crisis which bought down the Ming dynasty.
Throughout the 18th and nineteenth centuries the population of China quadrupled meaning that all marginal land was brought into prediction, the introduction of non food crops like Tobacco and Opium making food sufficiency more precarious. The country was therefore more vulnerable to a series of natural disasters, drought, earthquakes and a series of popular rebellions, white lotus, taiping mobilised, and killed millions. The bureaucratic infrastructure that enabled the emperors to rule broke down under the pressure of population growth and these disasters, meaning that self interested corrupt local bureaucrats increased their power.
By the time the Brits arrived with their gunboats the Chinese economy, and government were already weak, it was the shambolic response of an Emperor trying to mobilise local officials that meant that the British could probably have achieved their objectives even without their guns.
So a far more complex picture than you present, and perhaps there are some lessons there........
More importantly the population q