There's various reasons but the main reasons were:

China was a fractured and extremely unstable country at the time.

During this time period, it was trying to resist, ultimately futilely, against European colonial encroachment, eventually signing several very unfavorable treaties and even giving up land rights to European power.

Having another country essentially seize land in your country is incredibly significant. It sets a terrible precedent for the future when other countries come looking for easy pickings.

Even ignoring the disruption to order that Europeans were causing along the coasts and most profitable trading ports, the inner-China situation was not much better.

Imperial influence was waning, more so the farther one was from the capital and the coasts. Many magistrates were busy fighting rebels and bandits. This was assuming they weren't too busy consolidating their own power in their respective regions.

Some local officials saw that the end of the Empire was nigh, so they readied themselves for the chaotic times to come and for good or bad, they were becoming warlords, completely ignoring commands from the capital.

Even loyalist officials were not much help because they were most likely heavily entrenched in the system of bribery and corruption. Corruption was crippling on the Empire, draining it of resources and filling it with officials who were more concerned with politicking than with the day to day care of their people.

China's upper echelons were also very conservative and traditionalist.

First, discount the idea that the Chinese believed they were 'all superior' and didn't need to adapt new technologies. I can almost guarentee that no Chinese general looked at firearm wielding European armies or European artillery and thought 'no, I wouldn't want those'.

That being said, there were those who believed Chinese culture and wisdom to be superior to European, though not necessarily in certain areas of knowledge, but that is another discussion. Lots of rationalization was at work, enough said.

Many, in various offices of power, resisted the idea of modernizing, mostly because of the implicit change in how power would be distributed if they let modern ideas influence their governance. They were afraid of losing influence and so many developed a hardliner approach to anything Western and modern.

There was of course the association of modern technology with Western influences. The very same Westerners who were tearing their country apart, importing opium, extorting them in trade and resources. This was another strong arguing point for those who didn't want to modernize.

There was also the idea that adopting Western technology almost certainly meant also adopting Western mannerisms and culture. There were traditionalists who were afraid of losing cultural identity and make it easier for the Chinese to be assimilated as a European colony, essentially the destruction of the Chinese people.

Also, there was the popular sentiment of the time was to throw out the Westerners. During riots and uprisings, those who were European sympathizers could definitely become targets of mob lynchings. This culminated in events like the Boxer Rebellion.

Finally, there were pushes by the Chinese to modernize, particularly in the military areas after they had the resolve that they would need to fight the Europeans if they wanted to keep their freedom and significance as a nation state.

But these efforts were held back because of the many of the same reasons they were slow to commit to action. Corruption hampered the process, Europeans often played factions within the Chinese court against one another, often to great monetary profit.

Rebellions and uprisings occupied much of and divided the attentions of the Chinese officials.

And self serving individuals saw to their own interests before those of the empire.

The result was a half assed modernized army that was under equipped, often bought from the very same Europeans they were trying to fend off, lining the pockets of opportunistic merchants and European powers.

The governing system had very few wishy washy reforms that amounted to nothing.

And industry was chaotic, with little to no real technological advancement across the board.

The main reason Japan showed some serious results with technology was because the courts and the Emperor committed the entire nation to the process.

The Meiji Reforms were this famous top-down reformation of the nation, where change was brought out from high above and decreed to the masses below, rather than the more usual revolutionary, bottom-up change.

Japan faced its own set of problems during this time however.

There were plenty of traditionalists and conservative elements, just like in China, that resisted such radical, sudden change. Many believed it would promote chaos and disrupt order while others feared aggressive cultural assimilation by the Europeans.

These elements were mostly made up of samurai, the venerable warrior caste.

What's important to note is that the samurai had not been to any major warfare for over 300 years. By this time period, most were clerks, officials, and farmers (most samurai during any time period were usually farmers, or land owners).

They sensed that they would lose their honored place in society and thus, lose much of their influence, which is why they revolted in several very notable uprisings. These uprisings were the very loose inspirations for the film The Last Samurai.

So essentially, the top forced reform on the bottom masses and when met with resistance, crushed that resistance with heavy armed tactics, including assassination, imprisonment, and military crackdowns.

The importance is how committed Japan was to this change.

This is an extremely simple and general answer and there is so much more in this time period. But these are the general reasons.

Feel free to ask more questions.

Cheers!