To answer some of your questions:
1. Long lists are pretty painless to implement. There a some helper views included for building list views that aren't backed by in memory lists, and they feel really nice and fluid (https://api.flutter.dev/flutter/widgets/ListView/ListView.bu...)
2. Flutter has lots of built in animation support. Almost every aspect of a view is animatable out of the box (see https://api.flutter.dev/flutter/widgets/AnimatedContainer-cl... for an example). I definitely got carried away with the animations because of how fun and easy they were!
3. I had to deal with native code for push notifications, sharing flows, and universal links. Google publishes libraries for dealing with a lot of the common stuff, and there's great community support as well.