As someone who has written plenty of Java and JavaScript, Dart feels way more enjoyable to write. It just does. Maybe it's because I was less experienced when starting with Java and JavaScript, but it felt like there was a much smaller learning curve with Dart, too. I imagine it helps that I'm writing it in Android Studio, a JetBrains product, but I find the ergonomics better than even Kotlin. If you want to use it outside Flutter, you probably will wish it had a larger ecosystem, depending on what you're trying to write.