The problem I have with shepherding is when the player has no interest whatsoever in playing the ball, their sole interest is in blocking the opponent often so much so that they aren't even getting closer to the ball, just shuffling along, crouched over slightly to lower their centre of gravity, holding arms out to stop the guy going round them.
I don't have a problem with players shielding the ball in cases where they have/are actually going to play it (e.g. when you see the team in the lead go into the corner at the end of the match, ball being touched, sometimes attempt to play off the defender for a throw in/corner etc).