From a developer POV it's about the difference with the other platforms. If Apple provides a platform that bring the dev 50% more profit than the status quo, sure taking a cut of that extra profit could make sense.

If that same dev would have made the same profits on other competing platforms, Apple is just fragmenting the market and it's take should be limited to basically management fees.

I hope this new platform brings newer applications and innovations, but also expect competition to adjust, making it a situation where Apple is just one of the many platforms.