They do have 1+B people long ago.
Science and technology need the soil of IP protection, justice system and other core values (that CCP does not respect or care) to grow. You think talents would like to stay in a closed system like that? Think about it again after checking out situation in Hong Kong last year.
Only in some science branches, e.g. nuclear physics. But not microprocessors.
Also, scientific power is not the same as developed market. USSR was scientifically strong, but economically weak, ask ex-Soviet citizens how the 1980s looked like - an era of queues for basic necessities.
The Soviet Union was still the #2 economy too. And while it was behind in microprocessors, it was ahead in other branches, for example phage therapy and some fields of metallurgy. So it is correct to say that it was #2.
> Their growth is slowing, they've got major structural issues internally,
Those exact words has been making the headlines in the newspapers since 1989 at least, every single year, and yet here we are today, at the point where the US is willing to dismantle half of the global trade only to stop China from accessing whatever useful technology it still has not bought in the West.
> from accessing whatever useful technology it still has not bought in the West.
Or stolen.
Examples among many other include Nortel/Huawei, Chinese state hackers trying to get into ASML.
And whenever a company wants to do business in China, they need to create a subsidiary in China. The Chinese communist party has a fellow embedded in said subsidiary, and they can veto anything.
Pakistan, Nigeria, and a host of other countries have large populations.
Education and wealth matter a lot. If China can spread this out, then we'll be talking. As it stands, their educated middle class is very concentrated.
Their growth is slowing, they've got major structural issues internally, and the rest of the world is uniting against them.
The US and the West are going to stop playing nice.