China lagged behind the rest of the world during that period because she isolated herself for hundreds of years before that period. Whilst the rest of the world (especially European countries) were open to foreign ideas, new inventions, different styles of governance from the time of the Reformation, China locked herself in, aloof, ethnocentrically smirking in her advanced culture while snubbing the rest of the world as barbarians without a culture. Because of this widely held attitude, the rest of the world surged ahead in technology and social interaction. When the Poms arrived in China, the Celestial Kingdom was still a medieval society with lord/serf styles of governance over her provinces. whereas England was already an industrialized nation with democratic parliament. China was still mired in their "kowtow" ways of treating foreign vassal states and their visitors, England was current with the rest of the advanced nations who practice exchange of foreign embassies and consulates. English companies used banks to transact foreign currencies for international trade, China was still using taels of silver and her banks did not have any idea in foreign currency exchange. Stop blaming foreigners for weaknesses and shortcomings borne from domestic inadequacies. The Chinese loved opium and desired it highly. The Brits (and a handful of foreign devils) just were able to ship in cheaper opium from India, and flooded the market with "affordable" Ah piang, to be enjoyed by the masses!
Cheers!