I want to remove the "Focus" app from my iphone. How can I do this?

Focus is not more an app than Location Services or Accessibilty are apps.

Go to Settings>Focus and select each Focus profile. Go to the bottom of the screen and delete it. You can do that for all but the one called “Do Not Disturb”. For that one, make sure there are not schedules set up. If you do that, it should stay out of your way.

You cannot do this.

Simply do not use its capabilities.