alt Hacker NewsI saw that - and it doesn't seem to fit the bill. First, Dart is a language, not a GUI toolkit; and Flutter seems to be focused on Dart. It also seems to be opinionated in other ways in the introduction, rather than exemplifying its flexibility and adaptability to _your_ platform, programming language etc. Most importantly, it seems it will get you to produce apps whose UI fits a mobile phone rather than a desktop. I also get the sense that Google has strong control over this project.
Maybe I'm mis-perceiving - but that's the impression the flutter.dev site gives people.
Dart is the language flutter (the gui toolkit) is written in.
I've no idea what you mean regarding: "rather than exemplifying its flexibility and adaptability to _your_ platform, programming language etc".
It can produced mobile, web, or desktop apps from the same codebase... Dart and flutter are open source projects supported by Google, like android and go lang.
Seems like you're looking for excuses not to use dart/flutter. That's fine but you could just say you don't want to use them.