You turn Focus off in the Control Center. Tap the circular icon on the Focus button. Don't tap the word, just the icon. Don't press and hold. It's actually faster than the old toggle where you had to open settings and find DND. This, you can do from any screen.
And, nobody but the creator can understand this menu. More complex doesn’t mean better. I don’t want to be focused. I want my DND toggle back. Give us back our toggle back !
I think there was more than one creator of Focus. And the change has provided a lot of frequently requested options. Yes, it takes a little bit of time to learn how to use it but, once you do, it's great.
However, if you want things to be as close to the limited features of DND, you can do that.
Go to Settings>Focus. Tap on each of the options (e.g. work), go to the bottom of the screen and tap the delte button. Do that for everything except DND (and maybe Driving).
Go to Settings>Focus>Do Not Disturb>People. Select Silence Notifications From. Make sure you have not added any people to the list. Also, for Phone Calls>Allow Calls From, select Allowed People only.
In Settings>Focus>Do Not Disturb, make sure that Smart Activation is off and you have no schedule set.
Once you do these steps (and you only have to do them once), you can toggle DND on and off from the Control Center and it will work exactly as it always did.