All players have bad games, and all players have bad consecutive games. Even the likes of Maradona and Pele had awful displays, but you wouldn't categorise them as "rubbish" based on seeing those performances, even if it was the first time you'd seen them play. Obviously, I'm not comparing Kuyt to Pele or Maradona, but the point is still valid.
There ARE players out there (fumaca) who you watch and think "christ, has he even kicked a ball before?", I agree. But Kuyt is NOT one of those players. His two displays in the world cup were below expectations, yes. But they weren't so bad that they were beyond the point of being dismissible as just "two bad games" and nothing more. They certainly weren't so bad that you could immediately categorise him as being "rubbish" or "simply not good enough" without seeing more.
People are swift enough to judge him based on his performances against two of the most solid teams in world football. What would the reaction be if he failed to score against Wigan and Villa?