In particular, this means that if you're running an Android app on an older device, it can still show the latest Material design widgets (and similarly for iOS, showing the latest Cupertino styled widgets, or Material).
You see, this is rarely what I want. I’ve seen time and time again people trying to emulate controls and it just doesn’t work. Apple has a whole team that’s spent years making the iOS UI look just the way it is, and I don’t trust any other team to be able to copy this without serious effort. Sure, it might look pretty similar, but something always doesn’t work: the control behaves differently, isn’t accessible, animates incorrectly, etc.
I encourage you to compare our iOS ("cupertino") widgets with the UiKit ones. We've still got many to implement, but I think we have the fidelity pretty high for the ones we've implemented. If you disagree please do file bugs, we care very much about fidelity.
[1] https://play.google.com/store/apps/details?id=io.flutter.dem...
It also makes it very easy for developers to create their own custom widgets/layouts that are pretty challenging to achieve in other platforms.
I hope you'll give it a try some time - if nothing else, you might be able to raise some issues to help us improve some of those details!