The Dart part is a definite deal breaker
For a project I'm currently using C++ with Qt to have a single codebase for a client application that works on desktop, embedded (~Linux) and mobile. While styling the app for mobile requires a bit of stylesheet work, this is basically just CSS and fits with the customisation already desirable for the other platforms. The only niggle is really that the Android NDK doesn't offer all of the APIs, so I had to add some Java code and JNI action to obtain a list of media files and use Java APIs to convert the content:// URIs to a proper path which native code can use.
Beyond that, using Qt Android is a pretty decent experience that allows you to port a desktop GUI app to mobile without too much trouble, and without learning a new programming language.
Flutter holds zero appeal in comparison. It isn't stable on desktop platforms yet. It requires one learns new paradigms for the GUI and a new programming language, while bloating up the development flow with more tools and processes. And on top of that it's a Google project, which means it has the expected lifespan of a mayfly.
Not sure when or where one would use Flutter (or Skia) if one doesn't work at Google.