The text discusses how modern concurrency APIs in mobile applications can help improve performance by detecting and offloading non-UI work from the main thread, which handles drawing the UI and responding to user actions. The main thread can become busy and delay subsequent UI renders if it's kept occupied with unrelated work, leading to issues such as dropped frames, janky animations, and unresponsive UIs. Sentry, a performance monitoring tool, can help identify these issues by detecting dropped frames and suggesting tasks that can be moved off the main thread. By offloading non-UI work to background threads, apps can maintain smooth UX and respond quickly to user interactions, making them more engaging and efficient.