If you don't like the Plex app due to unintentional errors, you can uninstall it simply by going to the FireStick homepage. First, select the menu and go to the settings, and from here, select the application icon. From here, select the "Manage installed application" and click on uninstall the application. This way, you will be able to uninstall the application easily, and the app will be removed from the Fire Stick.