I am not developing on Apple platforms, but just like any reactive UI framework, i am almost certain the documentation of SwiftUI starts with a massive red flag

I am not developing on Apple platforms, but just like any reactive UI framework, i am almost certain the documentation of SwiftUI starts with a massive red flag that says "make your updates granular and don't repost a whole ass struct on every frame" at the very beginning which is exactly what the author seems to be doing. If all you want is a declarative UI, just dump in ImGui and be done with it.