I am not sure that's accurate. UAE and Saudi are monarchies.
Singapore is very socialist, if you look at their housing policy, it's entirely run by the state. They even allocate apartment to ensure that different ethnic groups mix.
https://www.youtube.com/watch?v=2cjPgNBNeLU
Also, I would not consider China poor today, and certainly even less so in the future.
This is not as hot of a take as you think. Many reactionaries believe that a monarchy under a good monarch is the ideal government system - much better than a democracy where uninformed voters make so many decisions
Singapore is ranked 3rd in the world by PPP, at $100k
The United States is ranked 10th with at $62k
I can come with with hundreds of criteria by which US is laughable, take foreign debt for example, or number of people dying from preventable diseases.
China has a capitalist market economy. They do have some degree of government ownership of companies and the government has asserted that they are not capitalist as the communist party is in charge and they have to maintain face. However, in practice, they are on the capitalist spectrum. Also, monarchies can be capitalist. Capitalism just means the state doesn't own everything and collect all the profits.
Also, I would not consider China poor today, and certainly even less so in the future.