I take away a different lesson: Dart is most likely slow out of the box. The author lists several reasons: int vs. Int64, GC interrupts, load hoist optimization

I take away a different lesson: Dart is most likely slow out of the box. The author lists several reasons: int vs. Int64, GC interrupts, load hoist optimization. All of these are issues with Dart. Hence microbenchmarks, even without interpretation or validation, point to issues with the language implementation. They are not "meaningless". It is true, one microbenchmark only shows that said microbenchmark is slow, not that the language as a whole is slow, but the plural of anecdotes is data. If you systematically evaluate a representative set of microbenchmarks (as in the Computer Language Shootout), then it is proof that the language is slow or fast. Now of course one can argue about what is "representative", but taking random samples of code from across GitHub seems like a reasonable approach. And of course there is the issue of 1-1 translation but at this point LLM's can do that.