I get your sentiment, but I feel like your view on iPads and there being no musicianship to it is just wrong. The instruments in garage band have velocity sensitivity and can be played expressively by tapping the screen just as you can tap the keys on a piano or hit the marimba with some mallets.

In fact on some of the synthesizers you gain an additional mode of expressiveness because you can adjust your input as you're playing notes, similar to MPE synthesizers like the Osmose.

An iPad is more than sufficient for making music.

I say this as someone that really enjoys playing my instruments (mostly guitars) and wouldn't trade the experience for an iPad ever.

Luckily, I can have both.