Are some people and companies using it? Sure. Some are still using JS/React and Xamarin too.

From an iOS perspective, do I see the majority of iOS applications written using Flutter? Nope.

Do I see jobs for Flutter developers outweighing those of traditional iOS/Android developers? Nope.

Do I tend to see more corporate interest these days in technologies like Jetpack Compose and Kotlin MultiPlatform than Flutter? Yes.

As such, I guess it depends on what you mean by "aging well".