Focus doesn't shut off all apps

Turn on or schedule a Focus on iPhone

1. Open Control Center, tap Focus, then tap the Focus you want to turn on (for example, Do Not Disturb). ... 
2. To choose an ending point for the Focus, tap , select an option (such as “For 1 hour” or “Until I leave this location”), then tap.

Turn on or schedule a Focus on iPhone - Apple Support (IN)

Unfortunately, Discord isn't a native app listed in Focus settings. However, you can silence Discord notifications directly within the app:

1. Open the Discord app.
2. Tap on your profile picture in the bottom right corner.
3. Navigate to "Settings" > "Notifications."
4. Here you can customize notification sounds, vibrations, and choose when you want to receive them (e.g., never, mentions only).

Please look at your settings...

Repeated Calls: If someone calls you twice within three minutes, the second call isn't silenced.

Please see the pic below which is self-explanatory

• You have allowed certain notifications to bypass Do Not Disturb. By default, phone calls, text messages, and FaceTime calls will still ring or vibrate when Do Not Disturb is on. However, you can also allow other notifications to bypass Do Not Disturb by going to Settings > Focus> Do Not Disturb > Allow Notifications and selecting the apps and contacts that you want to be able to notify you even when Do Not Disturb is turned on.
• You have enabled System Haptics. System Haptics provides haptic feedback for certain actions, such as when you touch and hold an app icon or scroll through a list. Even if Do Not Disturb is on, your iPhone will still vibrate for System Haptics if you have enabled it. To disable System Haptics, go to Settings > Sounds & Haptics and turn off System Haptics.

I understand your frustration with the changes in the "Do Not Disturb" feature, now known as "Focus," on your iPhone 7 Plus. While I can't directly address Apple's decisions, I can only say that...

Change is difficult to adapt to because it disrupts our comfort zones, introduces uncertainty and fear of the unknown, challenges our sense of identity, and involves letting go of the familiar. However, it's important to recognize that change is an inevitable part of life, and learning to adapt and embrace it is crucial for personal growth and development. With time, patience, and a willingness to explore new possibilities, we can navigate the difficulties of change and find ways to thrive in new circumstances.