I totally understand why you'd feel like this, but I think there are two big reasons why this is only true to a lesser extent with RN:
1) There are a ton of native APIs that accomplish exactly the same things, but have different APIs because different people built them and there's no pressure to make them consistent. Examples: layouting (just calculate x, y, width, height's of a view tree), animation, storage, networking, touch handling, the list goes on... it's a waste to have to learn the implementation specific quirks of each platform.
2) We've focused on making sure we can make apps at least as good as the native ones for the platform. Specifically this has meant exposing platform specific apis (e.g. Android's material touch ripple, iOS's gaussian blurs, etc), allowing arbitrary new ones to be added, and encouraging designers to still design their apps for each platform individually.
1) There are a ton of native APIs that accomplish exactly the same things, but have different APIs because different people built them and there's no pressure to make them consistent. Examples: layouting (just calculate x, y, width, height's of a view tree), animation, storage, networking, touch handling, the list goes on... it's a waste to have to learn the implementation specific quirks of each platform.
2) We've focused on making sure we can make apps at least as good as the native ones for the platform. Specifically this has meant exposing platform specific apis (e.g. Android's material touch ripple, iOS's gaussian blurs, etc), allowing arbitrary new ones to be added, and encouraging designers to still design their apps for each platform individually.