The best way of hampering China technologically has always been about keeping them completely dependent on foreign chip supply chain, e.g. ASML, TSMC, NVDA, ARM, AVGO, INTC, etc.
If you simply ban them from getting any western chips or chip tech you simply light a viciously hot fire underneath them to develop their own TSMC equivalent and their own chip designers, and we are now seeing them catching up rapidly. In fact, they are pretty close to catching up now, basically within one or two years...
The best reason to NOT ban exports is that it really doesn't work against a peer state, and China is close enough now to count. Given the significant economic trouble in the PRC (youth unemployment, unwinding the property bubble, overproduction of EVs) the US could definitely have played this better instead of creating a vibrant full-stack domestic AI sector in China.
They hired old asml employees.
This has crashed, check the markets.
They do not need a ban to light a fire under them. The fire is already lit and burning and nothing the west can do will even slightly dampen it.
You yourself claim they are within a couple of years. If that's the case you think they will stop developing if we sell them chips? That's laughable.