The Great Wall was not very effective. China has been successfully invaded many times, including (but not limited to) the Jurchen, Mongols, Manchus and many many others.
And the Great Wall is an exception. Most walls were around cities, not countries.
Border control was practically impossible until the very modern era (last 100 years or so). The infrastructure for controlling borders only became possible due to technology.
I prefer NewPipe to Revanced.