I think like most hookers, Luke gets a hand from dodgy plays and interfering with the marker but he is still a genuinely dangerous player. he is elusive and surprisingly strong for a man of his size. even if the NRL cracked on all those things he'd still be one of the most dangerous dummy-half runners in the game.
and apart from that, when we're talking about his quality as a player why does it matter that he succeeds because he exploits the status quo? that is like complaining that Smith is only a superb defender because referees don't crack down on wrestling in the ruck and therefore let him get away with a variety of tactics that he is famous for. It doesn't really change how good they are. It is just complaining because those players have managed to adapt better to the way the game is played.
every hooker in the NRL tries to take advantage of illegal tactics in the play-the-ball and various ways of interfering with the marker. It isn't like all the other hookers in the NRL are trying to play the game in the right spirit and Luke is just being a dodgy ****. they all do it and Luke is just particularly adept at it. Good players and winners learn how to take advantage of the situation, while losers just whinge about how its not fair.