- Dart 2 has a sound type system and the compiler has been receiving lots of optimisations based on types since then (several years now). So this is no longer true.

- that's currently true but in the next release (at least that's what the Dart team have been working on for the past several months) it will have nullable types just like Kotlin.

- That's a strange criticism. Dart has excellent constructor syntax, I don't know a language that is more flexible with constructors.

e.g.

    class Person {
        String name;
        int age;
        Person(this.name, this.age);
        String toString() => "Person($name, $age)";
    }

    main() => print(Person("Joe", 40));

Looks pretty good compared to most other languages?!