Why is a flashlight app even necessary? Most modern phones have a quick-settings button for the flashlight already. If your's doesn't, you can easily add the functionality with
MacroDroid, which also gives you multiple ways of triggering the light on/off (e.g., gesture, shake, floating button, widget, or even add a custom quick-settings button). If you don't care for MacroDroid, I'm sure you can do something similar with Tasker or Automate. The beauty of these apps is that they don't just serve a single purpose.