I'm glad Flutter is not changing design to support this M3Expressive [1] right off the bat. One of the biggest problems with Flutter for me is just a lack of alternative design systems (compared with web frameworks) or the ability to easily spin off your own design system. And it's ok to use default Flutter's design system (which is Material Design), but the need to conform to whatever the Google design team comes up with in the next update wasn't great.
Components' renaming (RaisedButton -> ElevatedButton, wtf - was it really worth millions of person-hours of renaming in hundreds of thousands of Flutter codebases?), apps suddenly becoming pinkish, until developers frantically updated code setting `useMaterial3: false` just to stop apps being suddenly ugly, etc. I.e., it's fine for the design system to change and evolve, but with Flutter, all control over the app's look is virtually taken away from developers who use default material widgets. You just update the Flutter version and pray that your app didn't change in a way that was never expected.
It would be good to have Material 3 Expressive as a separate design system, for sure.
But pinkish is just the default. You can select a color scheme and theme color like blue, indigo, etc. Looks better off the bat.