I prefer C#/F# over Dart, but Flutter is promising, and I continue to check in once and a while. I usually overcome PL preferences when the platform or toolkit is compelling. I remember Notch (of Minecraft fame) adopted Dart very early on, and I actually tried it out back then. Somebody had written a Lisp in Dart. I really like F#, and it seems to be sidelined all the time with .NET. There are more and more ways to write C# in a functional way, and it has become the lingua franca of many game engine/3D media creation tools like Unity, Wave Engine, Flax, and Stride to name a few.