Why do you think Wilberforce expressed his inadequacy for the task he had taken on?

Wilberforce reported as an inadequacy of the teachings of Christianity among ignorant Christians, because they didn't study the Bible consciously enough or deep enough; and he denounced the Evangelical view of human nature as depraved and corrupt.

He considered such ignorance as a failure to appreciate the importance of the sacrifice of Jesus to reunite humans to God, and gain salvation.