Pretty obvious that China is not the power they claim, they can’t even control tiny North Korea. This has to be very embarrassing for China, showing the entire world they are powerless to stop North Korea.
They aren’t powerless. They just don’t want to. China is fully aware change in NK doesn’t go their way. Imagine a fully industrialized Korean Peninsula with access to the full resources and rare earth minerals at China’s doorstep. An economic rival and brain drain border. They can’t have that.