In my view, if a priest can't begin praying over the upcoming Sunday readings a week in advance, keep them in his heart while inviting the inspiration of the Holy Spirit, and preach them from his gut for ten minutes on a Sunday morning, then he should let somebody preach who knows how.
The reason Protestant preachers are generally better than Catholic priests are that preaching the Word is all they've got.
If they fail at that, who needs them?