No it's unprovable and completely unscientific, but reactions on this topic seems to prove that it's a widely shared opinion and a fact to consider if Google wants Flutter to succeed.
We all see the knee jerk reactions to Dart. Yet, most people who _actually_ try it tend to like it a lot. We've run actual studies and something like 98% of developers who haven't tried Dart have no strong opinion about it either way. (Which is not better nor worse than Java or TypeScript, which we benchmarked against.) We also run UX studies on Flutter API and tooling, and Dart is not an issue.
Dart is not an easy sell: it doesn't have a gimmick feature, it's just a well-balanced modern language. It was very fashionable to hate it a few years ago. But don't let the vocal minority distort your perception.
Not some support for other languages on a first class basis on the webpage just like Javascript (which direct access to the DOM and everything).
Besides, I'd much rather have the effort go into one new VM (or VM "mode"), so we can solve the problem once and for all. That is, let's have Web Assembly.
Having teams context switch to yet another syntax for basically another language with the same semantics is just not something people are excited to do.. and I think the same group of people google wants to easily appeal to with this language, are the same type of people who DON'T like switching languages often.
I would recommend checking out Unity if you're into making games.
When we started, about 3 years ago now, we looked at many languages (dozens of them) and, objectively, Dart was the best fit for what we wanted to build.
At the time, "we" was a few people from the Chrome team, and me (HTML spec editor at the time). We were all Web people, whose only impression of Dart was somewhat like negative comments in the thread here. When we studied each language, though, we found that impression was really not relevant to Dart as a language for mobile, and in fact it fared better in our comparisons than the other languages we looked at.
I think it would make a lot of sense for people to create other projects very similar to Flutter where Skia is combined not with the Dart VM but with other languages, and for the Flutter framework to be ported -- in a language-idiomatic manner -- to those other languages. I can totally imagine, for instance, a TypeScript-based UI framework like Flutter, or a Kotlin-based UI framework like Flutter, or a Swift-based UI framework like Flutter. After all, in many ways, Flutter is just an evolution of previous UI frameworks like React, DOM/CSS, UIKit, and Android views.
Let a thousand flowers bloom. One day I hope I can write my mobile apps in FreePascal using a reactive framework with a design evolved from Flutter. :-)
Obviously every company will be self-serving in its technology choices. But it seems to me that people got the feeling that Google was doing themselves a favour, more than doing everyone a favour.