I've heard this before, and I've also seen IntelliSense labelled as a crutch. I don't understand this - how does IntelliSense prevent mastery of a language? Doe

I've heard this before, and I've also seen IntelliSense labelled as a crutch. I don't understand this - how does IntelliSense prevent mastery of a language? Does it make a difference if someone's mastery of a language involves them using IntelliSense?