Generic iOS device

The Generic iOS Device, under the Build Only Device section of the Device and Simulator drop-down menu, is used for when you need to archive your app, which means that you are preparing your app for submission to Apple (either to the App Store or Test Flight). If you try to select Generic iOS Device now and run the app, you will get the following message:

Therefore, change Generic iOS Device to an actual simulator, and then you will be able to continue.