Playing the game of economy well enough for everyone in the world to acknowledge its success requires a great power as a carrier. Although the Han Empire of 200 AD is not that great of a carrier, it does meet all the criteria of a great power.
More importantly, at this time, it's essentially an initial natural economy. Under such circumstances, small tweaks and fixes can be made gradually. You could even bring in someone who's studied economics a bit, and there's no way they'd mess it up. The cornerstone of a natural economy is self-sufficiency!
That's why Chen Xi is confident to play slowly, to gradually explore and discover the system he needs. He has already steeled himself to spend ten years on primary reforms, and then another thirty fiddling around to observe nature's evolutionary laws. After all, he's only in his early twenties, and has plenty of time!
