Why is the goal to get rich? That seems lame and shortsighted
How about having the goals of developing healthcare instead of "being rich"
Consider healthcare, usually older people need it more than younger people. If you have a higher proportion of older people in a population compared to younger people, you have a larger proportion of the associated costs being carried by a smaller proportion of the population, this means decreasing healthcare quality, increasing the pool of people paying in by increasing retirement age or increasing taxes. None of which are particularly good.
By far in poor countries healthcare is much more affordable than in rich countries. I think one of the main outcomes of rich countries is just increased costs for everything.
Would you rather old people be dying of starvation/due to lack of healthcare because the country isn't rich enough to support them fully than living in old age homes?
Look at how the poor in India live. "Getting rich" does not mean becoming multimillionaire, it just means reaching a developed country's standard of living.
Mobility is, in the modern world, as much a political argument as an economic one.
A country can be "highly mobile" with flat GDP and limited income growth opportunity for the individual. That is just how the math works out. Social mobility is a term-of-art that does not mean what most people intuit it to mean.