It is difficult to defend footwork- Slater and Stewart are actually probably the 2 best at it, whist Bowen does it through speed. That said a fullback is on a hiding to nothing, you are flat footed as a fullback, the attacker has all the momentum, don't pretend it is not difficult to stop the attacker- it is. It is why Slater is seen as what he is- he saves as many as he scores.
Are you seious? Where did I say it wasn't difficult lol.
You said it was NEAR IMPOSSIBLE to do. Near impossible would imply that it's rarely done, i see it all the time.