In many senses there's hubris in the western* view of China accomplishments: most of what western companies have created has had significant contribution by Chinese scientists or manufacturing, without which those companies would have nothing. If you look at the names of AI researchers there's a strong pattern even if some are currently plying their trade in the west.
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* I hate the term "western" because some "westeners" use it to separated what they think are "civilized" from "uncivilized", hence for them LATAM is not "western" even though everything about LATAM countries is western.
It's worked for a very long time for aircraft.
China has been pushing to build its own aircraft for >23 years. It took 14 years for COMAC to get its first regional jet flying commercial flights on a Chinese airline, and 21 years to get a narrow-body plane flying a commercial flight on a Chinese airline.
If for no technical reasons and purely political, COMAC may still be decades away from being able to fly to most of the world.
Likewise, in ~5 years, China may be able to build Chips that are as good as Nvidia after Nvidia's 90% profit margin - i.e. they are 1/10th as good for the price - but since they can buy them for cost - they're they same price for performance and good enough.
If for purely political reasons, China may never be able to export these chips to most of the world - which limits their scale - which makes it harder to make them cost effective compared to Western chips.
This doesn't matter so much for military purposes: they can easily eat the cost of a higher maintenance and replacement schedule on a smaller number of military jets with fewer hours on them.
This gives them more iteration cycles, speeding their building up of experience. They're catching up. Industrial espionage will help them along too, but not as much as the experience from engineering their own designs.