Dart is a decent language for Flutter, but I’m not sure why you’d want to use it off of the flutter path. Maybe for CLI or other client-side tools? Either way, if you’re not re-using a dart package or using flutter, you absolutely should not pick it as your tool of choice.
The language seems nice syntactically, but I find it really frustrating in practice. It’s good enough for the “happy path” that was envisioned - basic UI hierarchies. It’s clear some team designed the language by first writing examples of what they wanted it to look like when making a UI. I think Swift UI caused similar complexities on Swift. You can confirm that even the contributors think this from reading controversial PRs in GitHub.
The nice thing about flutter, and Dart, is that it’s starting to take a life on outside Google. Google should hand off ownership to a foundation or other organization - especially now that their newest thing is Kotlin Multiplatform. I hear more and more companies writing flutter backends for their UI work, so hopefully it could survive alternative stewardship. I believe some TVs and car navigation systems now use flutter, plus all the google stuff.
Which ones? Flutter is quite good, especially compared to things like Java Swing or GTK.
If there were major other entities seeking to participate in its development and advancement I could see a reason to change things, but that doesn't seem to be the case.
I think that Google should explicitly encourage and support the ecosystem by moving key tooling to a third party foundation, even if staffed by their employees - eg. the pub.dev package manager could be maintained independently and get a team dedicated to it. Google would be then free to drop support, or change direction, without dragging this great ecosystem down to stagnate.
Golang/Kotlin are seeing strong, and continued, support amongst their owners, and their support isn't questioned. That said, many people have questioned the direction of Golang because the only maintainers are Google employees, and they don't listen to much outside opinions for direction.