Because he feared hardships, he never properly trained in martial arts until the age of fifteen. His body wasn't conditioned, and thus he couldn't unleash the effects of the Channel-opening Pill to become Transcendent.
His father was a Great General of Li Country, always leading troops in the field, battling for both country and family, and had little time to discipline him.
He would have lived his life as a wealthy idler, passing his days in peace.
But as the saying goes, "Pottery is bound to break at the wellside, and generals are bound to die in battle."
When Fan Wushu's father retired from the battlefield, gravely wounded and on his deathbed... he was still indulging in the pleasures of a brothel and hadn't returned home.
His father clung to his last breath waiting for him, and before dying, he only said four words—
"Utterly without learning."
His eyes remained open in death.