If Nomads of the Steppe fail to control and rule China?

We were just talking about this in class

And this was my opinion

China's development would have never slowed down.

If the Mongols and Manchus never. Defeated the Han Chinese. And controlled China from a long time.

Both my class and teachers agreed. That before the Mongols ruled and defeated China. In the Tang and Song Dynasty it was powerful one of China's Golden ages. During these periods China

I also think if China was never defeated by the Mongols. They would have been powerful not to be defeated by the Manchu's as well. Meaning China would have never been weak. China would never had lost to the British. And later on China would have never turned to communism. China today would have been at least a Constitutional Monarchy.

What are your thoughts?