How can China be very advanced, but still remain a rather poorish country?

China is advancing fast in things like green technology, EV adoption, AI, but looking on bare data, the country in general is still rather poorish for Western standards.

The gdp per capita, adjusted for price levels (PPP), it still on the level of countries like Thailand and below the poorest states of Eastern Europe. The growth is also more or less around 5%, not bad, but it would take decades with that to even match the wealth of Rumania for example.

People often talk about Japan in the 1980s, for example, to describe the current state how the world looks at China with it's modern cities and infrastructure.
However, Japan at that point was already one of the richest countries in the world.