To me as someone who recently got into Flutter to make a side-project (mobile game) the most glaring problem isn't the lack of ecosystem or little UI issues the author mentions but the language itself. You had a green field to make the best programming language for creating UIs and you made Dart? Like what. I don't have particular issue with the heavy OOP paradigm but the fact you have to write so much boilerplate fe…
They didn’t create Dart for UI. It was dead and they shoehorned it into Flutter.
The APIs the OP are complaining about are Flutter's not Dart's. Flutter tried to do a vdom-like thing that also included styling on top of regular function call syntax and it is... what it is.