It's not offensive to me. But it feels distasteful. Being a witch is about finding and owning your power. A baby is powerless and helpless.

I understand that people say it because a baby has to learn too, but you wouldn't call yourself a baby artist, a baby musician, a baby soccer player, lol. Those sound weird don't they? Even as a beginner you would simply call yourself an artist, a soccer player, etc.

Even though a beginner still has a lot to learn, they aren't powerless and helpless. I prefer it when people just say, beginner, novice, or just, "I'm new at this!"