I am saying that trying to re-write the layout engine, data layer and all the rest to make it work the same on both platforms is not only a massive undertaking - it is ignoring the reason the platforms diverge to begin with.
iOS has features Android doesn't and vice versa. Something that works on both platforms is always going to be a second-class citizen - it's the lowest common denominator.
I don't want the lowest common denominator because it's 'easier for developers'. I want the best stuff.
The theoretical technical debt due to writing on different platforms is why we have software architects and senior developers.
Really, I've been part of a dev shop that does ios/android - the biggest hurdle is people problems, not code. People who don't know what a good app is or have any taste so they say first show me, then I will start asking for changes at random while insisting on a tight deadline.
As for web/ios/android/desktop - this is a rare bird, if you need to support that many platforms, you can afford an architect and some smart people.