Yes they are at risk by the sheer issue of not having a population. Population cliffs have killed major economies in the past and they will in the future. Buying up gold is all fine and dandy but gold is also heavy and takes up a ton of space so it isn't like you can trade with it all that well. What made gold shine was having a fiat conversion rate so they need either fiat to be strong or the gold only does so much.

With their nuclear fleet, they are building the types of reactors (salt-cooled) that the US messed with in the 60s and 70s. They work they are solid options but they have considerable drawbacks hence the reason we never saw them take over all those years ago. China is also still pumping out coal plants like its no tomorrow as well because certain regions of their economy rely on coal. SMR tech and more importantly fusion technology is what matters the most and the Chinese are incredibly behind in fusion.

So their AI is well extremely poor for worldwide adoption. It is only really good for ethnic and that is a huge huge problem to fix something that the rest of the world is focusing on while they aren't. Within AI they are still lightyears behind in making the most cutting-edge chips they can make the basic ones but the ones everyone wants their hands on they don't have the slightest ability to manufacture or get the tech to manufacture the cutting-edge ones.

China is huge on subsizing these industries as well to keep them afloat and move them forward and that only works if you can stop. When they have tried to stop they have run into huge issues so they can't. Overcapacity in manufacturing is also due to a lot of manufacturing from places like the US moving or expanding in other countries like India and Thailand. It isn't from being so good or being able to out produce rather its a lack of investment or reinvestment.

A prime example of this is China's EV fleet is "enormous" however what a lot of people do not know is that they "retire" the cars after a few months maybe a couple of years and there are huge car lots with practically brand new vehicles that just sit there. It allows the companies and country to say they are producing and purchasing all of these EVs but they do not use them at all.

BRICS itself is going to have issues in the future. China and India cannot decide on a border and have already had wars over it in the past. More recently they have had soldiers beating the other side to death with baseball bats with spikes so that is going to cause a split (India won't want China to have all the power) and Russia is burning through gold reserves as well as having transitioned their economy to a war based economy. Say they win Ukraine they face a huge issue with producing things they do not need anymore. Their economy is dependent on war to keep it functioning.

The long and short of it is China is building debt at a rate that makes the US look slow and they have no end in sight. Facing a population collapse means you can't pay it back due to your economy often shrinking (look at Japan for a comparison) and you run into economic dysfunction. China looks a lot better and put together than they are even their armed forces have had recent public embarrassments like the rockets being fueled with water and not actual fuel to shoot them.