As far as I know, Flutter dev evangelists are trying trying their best to push it into massive adoption.
One thing you may fail to see is the reason for RN's massive adoption, and those are
1. It was released before Flutter, 2015 compared to Flutter's 2017
2. No need to learn a new language. JavaScript is JavaScript. The initial thought of having to learn Dart (which is very similar to JavaScript and Java, but who'll know till they use it?) is a push back
3. RN's similarity to React. It is easier for devs who'd been using React to jump into it, and React has more adoption than Angular
In the end, users don't really care whatever you use. Does your app do what they want/expect?
Yeah, JavaScript and even React have such a critical mass of developer familiarity at this point that I don't see how they could be unseated without some really killer new advantage. Flutter's advantage is... it's a bit faster? Maybe? Maybe the warts when it comes to spanning the platform gap aren't quite as bad? I think it's going to take more than that.
One opportunity could be desktop. If Flutter can beat React Native to that (doesn't really look like it will so far), that could be a killer app. Right now people use Electron, which carries a couple of significant downsides.
1. It was released before Flutter, 2015 compared to Flutter's 2017
2. No need to learn a new language. JavaScript is JavaScript. The initial thought of having to learn Dart (which is very similar to JavaScript and Java, but who'll know till they use it?) is a push back
3. RN's similarity to React. It is easier for devs who'd been using React to jump into it, and React has more adoption than Angular
In the end, users don't really care whatever you use. Does your app do what they want/expect?