Frontend - Flutter for the UI (Android, iOS and Web) Backend REST Services - Pure Dart or Aqueduct.io for more complex apps Scripting on my PC Command Line Interfaces for different Tools Advent of Code solutions Blockchain stuff Chat bots ... much more
So why do I like Dart?
The default libraries are amazing - dart:convert, dart:io and more. The asynchronous language features like async, Future and Streams are the best ones I found in a language until now. The Dart and especially Flutter docs (just look at the animation curves section) as well as the official YouTube videos do a great job of teaching different subjects. The combination of dynamic and statically typed objects and variables works really well in most cases. The List and Map operators are really good and easy to use. Package management with pub works and is fast.
Disadvantages
The Ecosystem for non-mobile apps needs more libs.
Conclusion
Try Flutter and see if you like working with Dart, it's very easy to pick up.