Can’t drag and drop in Mojave 10.14.6

Try right-clicking or control-click on the items and select the Trash option on the pop-up menu.

It might be an issue with the Trackpad's settings. I have trouble dragging & dropping with the new Trackpads unless I uncheck the "Force" or "Haptic" Trackpad setting (I forget the exact name of the setting). This is the last setting on the first tab of the Trackpad System Preferences.

Restart in Safe Mode and see if drag and drop works.

Use safe mode to isolate issues with your Mac - Apple Support