Slow in adopting new functionalities and technologies
When a new version of Android or iOS is released, it introduces changes that take time for Google to incorporate into Flutter. While they may be relatively prompt for most updates, the dark mode for iOS devices remained incomplete by the end of 2021, despite being more than two years since the introduction of dark mode in iOS 13.
One of the drawbacks of using Flutter is that it requires delivering its own engine with every app, which can contribute to increased size, memory usage, and startup overhead.
When comparing Dart to languages like Kotlin or Swift, developers may consider Dart to be relatively simpler or less mature. In comparison, Kotlin and Swift offer more advanced features, a larger community, and a more extensive ecosystem. For me as a developer using Swift it feels as taking 10 steps back.
Flutter and Dart are products from Google. There is an high change they end up being killed. Google has a long history of killing products. You can build on that. See https://killedbygoogle.com
Smaller Community and Ecosystem
Compared to native development platforms, Flutter has a relatively smaller community and ecosystem. This means that finding solutions to specific problems or accessing comprehensive documentation and libraries may require more effort.
Limited UI Customisation
Flutter provides a wide range of pre-built widgets for UI development. However, if you have specific design requirements or intricate UI components, customising and fine-tuning them in Flutter may be more time-consuming and challenging compared to native development.