Flutter is a brilliant framework, despite what hardcore native devs of either platform might tell you. It has it's flaws, but the speed of its improvement and its usability as a cross-platform framework is probably the best on the market.

That combined with being able to just code native Android or iOS if you really have an issue you can't overcome make it quite powerful.

You're also plain wrong about Android. It is by far the largest platform in every country outside the first world, and is not going anywhere. You just have to look at Asia, Africa and South America to understand that around half the world use it.

I believe that iOS users tend to favor apps with beautiful designs, and Flutter's blank canvas gives developers the ability create expressive and unique UIs. If you're looking for an example check out Wonderous.app