If the Chinese government allowed free convertibility of RMB into other currencies that flood would turn into a tsunami.
IDK. Perhaps the current desperation has something to do with the lack of a convertibility. In an open trading regime, support for the yuan would come from the fact that you can buy a whole lot of stuff in the world’s largest economy - most of the world’s manufactured goods, rare earth elements, the labor of a billion people... Oh, and you can also sell your raw materials, energy, and financial services into a economy with apparently bottomless demand.
You can already buy anything you want from China (in dollars or RMB or most other currencies). You can sell most anything to China (and folks will be happy to pay you RMB and more than willing to pay in other internationally convertible currencies). The lack of convertibility is an effect of the Chinese government trying to stem the rush of money, not a cause.
How much have you actually interacted with the Chinese economy? Or people trying to get money out of China?
People are scared. Corporate debt is extremely high, a lot of it is to government sponsored entities. The viability of huge amounts of debt are predicated on an economy that is growing at 7% per year and dragging corporate profits and revenue along on the same growth trajectory. There are giant empty "
ghost cities" built around many tier 3 and tier 4 cities because real estate prices have been increasing so rapidly many people assume that just buying apartments and holding on to them, unoccupied, will eventually make them money and/or fear that if they wait to buy apartments for their children until those children are able to live independently they won't be able to afford to buy anything.
Before Xi Jinping, usually having wealth (and spending some of it on building and maintaining good relationships with local government officials) was good protection against losing everything, but now anyone in the public or private sectors could be the target of anti-corruption prosecution. Government officials are worried about being seen eating at too nice of restaurants, and always make a point of ordering take home packaging for any leftover food, even if they're not going to have the chance to eat it, to avoid seeming wasteful (leading to wasteful use of packaging, but that's another story).
People are afraid to use domestically produced baby formula because of contamination issue. If you're traveling to China and know someone who recently had children, US made formula or baby food will usually be an enthusiastically well received gift.
There is an impulse in some from the US to build China up into this unstoppable monolith. And what they're doing over there is indeed quite impressive. But don't make the mistake of seeing only the strengths and not the weaknesses.
There is a really significant reason China doesn't make their currency freely convertible and it's not something that they can change simply by changing government policy. It would (it will) take years of reform to give everyday and wealthy chinese people confidence in the soundness of the chinese legal system and economy before a freely convertible currency would not be a recipe for a run on the RMB.