I too hate cross-platform schlockware but it sounds like you are not familiar with the technology.
"controls are mapped to platform-specific native user interface elements; for example, a Xamarin.Forms Entry becomes a UITextView on iOS, an EditText on Android, and a TextBox on Windows."
You win some you lose some. With Fragments Xamarin actually extends support to earlier Android devices. Less of an issue now, but there was a time when this actually extended platform reach, reduced code, and simplified training/upgrades.
For some things it's about the common talk-to-the-backend code, not true-code-once across iOS/Android...