I also advise watching the Angular documentary, where they briefly describe being forced to adopt Dart by management was a friction point, only sorted by letting them go with TypeScript, and AngularDart be its own thing.
Eh, people critique the kitchen sink type system but at the end of the day that system is why TypeScript took over, not a weird add-on you have to put up with to get it. It's what makes it possible to assign comprehensive types to ~every JS library, which is what allows TypeScript to gradually eat the whole JS ecosystem.
Any other approach stops short of the goal of being JS+Types, which means you end up with a different language with different semantics, which is where Dart failed.
IMO Dart has become a niche Flutter language instead of a general-purpose language. Dart decided to focus on being a client-side language and it is very difficult to win over JS/TS.
Many times it isn't the quality of the programming language alone, rather external factors that trigger its adoption.
Not only Dart. Lit was completely abandoned without any public announcement. Killed by Google.
Also, I feel like Dart is a maximalist project. "Batteries included" also means a whole myriad of tools and libraries also at the grace of the Google Dart team.