While we'd love to be the best solution for every problem, it turns out the HTML-based web has been highly optimized for decades for text-heavy, linear, reading experiences.
So we're staying focused on the places where Flutter does the best job: interactive, non-linear, more-create-than-consume.
So our sites use HTML & CSS: flutter.dev, dart.dev, pub.dev
And our devtools are built in Flutter Web: https://docs.flutter.dev/development/tools/devtools/overview Along with web experiences from rows.com, reflection.app, rive.app, supernova.io, and many more.
FYI: I'm the product manager working on Flutter and Dart web tech at Google
(edit: fixed domain, mis-added one app)