No, it isn’t. Dart is a considerably bigger language than Go. More features = more effort to learn.
When it comes to ease of learning, it’s really, really hard to beat Go. Go is easier than Python, too.
However, the easiest language to learn is unquestionably Smalltalk. It virtually has no syntax! Smalltalk syntax is completely based on message passing between objects. That’s all there is to it!
In fact, the complete syntax can fit on a post card: