Thing is Dart is a shitty language with tradeoffs made specifically to make Flutter work well.

The terrible meta programming support shows in basic things such as JSON serialization. It's like Java--, I can't think of a reason to use it on backend over Java or Go.

It's not comparable to Javascript - despite it's warts, Javascript is very dynamic and when coupled with typescript that let's you do a lot of powerful things and describe it with the structural type system.

I have not used dart for a few years now but I've used it both when it was DartAngular and Dartium, and in flutter 2/3.

Don't get me wrong - the DX of writing flutter and fast reload is the best I've used in mobile space, but the language itself is terrible and I would not use it in any other scenario.