Getting rid of Focus altogether?

It is not an app that you can turn on/app or remove entirely. What you can do is choose each Focus State and remove any Schedule that has been added and also turn off Smart Activation, so it is not automatically enabled. By default there is no Schedule and Smart Activation is turned off, but you may have seen a message on the screen where it can be turned on and you inadvertently allowed that without realizing what it was going to do.

Some Focus States can be deleted, such as the Personal Focus where after you tap it at Settings > Focus > Personal, you can scroll to the bottom to Delete Focus. That is not possible on the Do Not Disturb focus state.

Since your tagline shows iOS 18, here is the User Guide specific to that version. Another setting you will want to review that is seen in that Support Article is Share Across Devices. With this on, a Focus change on one device will be reflected in all devices using that same Apple Account. Conversely if you have it turned off, then each device will have its own Setting so you may need to make that change on multiple devices.

Set up a Focus on iPhone - Apple Support

Turn on or schedule a Focus on iPhone - Apple Support

• Note: When you set up a Sleep Focus, it follows the sleep schedule you set in the Health app. To add or edit a sleep schedule, tap Open Sleep in Health. See Add or change sleep schedules in Health. You can also change your next bedtime and wake-up time. See Set an alarm in Clock.

Do Not Disturb was subsumed into Focus a while back.

It can’t be removed, but it can be ignored, and most of the focuses (scroll to the bottom of each) can be removed.