It's always a pain when an Android app triggers that "X Application isn't responding" dialog. The "Wait" option often doesn't work, making "Close app" the preferred choice for most users. To alleviate this, Google has simply taken that ANR dialog away from Android P. Instead, unresponsive apps will now automatically crash.

This new behavior was described on-stage at Google I/O '18's Android Protips session. Reto Meier, the presenter, discusses how crashing apps in certain scenarios isn't a brand-new thing. Meier goes on to explain how crashing the app instead of displaying an ANR dialog will encourage developers to fix whatever issue is causing the crash, even if it may not be better for the user.

Opinions on this change are mixed in the r/androiddev thread discussing it, though most appear to be critical of it. For those who aren't fans of this, there is an 'Always show crash dialog' option in Developer options that may be helpful.