Sandboxing won’t stop shady and illegal developers. Neither will review. The story of what happens to a platform when you allow any crap on it goes back as far as the original Atari 2600 to Android that has four times the market share but still less revenue for developers.

And yet the Google Play Store is fine. Is there more malware on it than Apple's App Store? Sure. But people use it every day, and the world hasn't fallen apart. They could certainly do more to root out malware, but that doesn't mean full-on gatekeeper with draconian rules like Apple has done.