This question was answered years ago by the magna carta. Without rule of law, you get corruption and a dissatisfied population. Then you get economic stagnation and suffering by the masses. Finally, you get the French Revolution, the various Communist revolutions, and so on.
Rule of law is necessary for economic prosperity because without rule of law, entrepreneurs cannot confidently engage in economic activity without fearing that their property rights will be trampled and the wealth they generate will be taken away by an arbitrarily deciding government. Why should someone take so much risk and then be punished for their success? Without rule of law, there can be a temporary party for a few decades, but the party stops when the government starts getting out of hand and abuses its power. This is why Xi Jiping is making stamping out corruption one of his top public priorities, more so than any previous Chinese leader in modern history. He is also on record that he wants China to move forward to have proper rule of law.
I dislike it when people bring up Singapore as an example. Singapore is so small that it's really easy to manage compared to a large country with a large population. And besides that, Singapore doesn't have poor quality rule of law compared to other countries (yet).
edit: I get the impression that you equate rule of law with democracy. But you didn't actually say that, so please confirm for me whether or not that's what you really think. Rule of law is something else entirely: https://en.wikipedia.org/wiki/Rule_of_law