You can't blame it all on BBall IQ/training.
Amare: Slow feet. Kind of like Allan Houston. Tremendous athlete, leaper, looks the part... but doesn't have the innate reaction time or anticipation to be a strong defender.
You could have a high BBall IQ, but just not have the physical tools. A good example was Mark Jackson (the mental game of a Jason Kidd with a soft plodding body) - that resulted in top college defender (he may have led the country in steals in his last year), but he was a below average defender in the NBA. Quick hands made up for the slow feet somewhat.
Carmelo has slow feet on D, but has quick hands and good anticipation. But he's had a tendency to be a little lazy with his arms down at his sides on D - a la David Lee... (he prescribes to the rule that getting a rebound is akin to playing defense - it keeps the ball away from the other team)