The multi-platform frameworks (dart-flutter, react-native, etc), are they effective? To what extent?

Been looking at dart-flutter relationship recently... seen what it can do... pretty amaizing! Two birds with one stone is real!

Before jumping to it, i soldem wonder;

• what are the compromises that one would face upon embarking this?
• can these comporises be that bad? (compared to native ios/android app dev)
• how bad are the work-arounds (if they exist) to these compromises?

PS: any extra information would be highly appretiated 😊