Why is my Apple ID greyed out

This has to do with screen time restrictions. Go to settings>screen time>content and privacy restrictions and make sure that the switch by allow account changes is on

You can also try and turn off screen time alltoegether.

After this, try and access your account settings again

If an app or feature on your device is not working, not appearing, or is restricted (grayed out), it may have been disabled using Screen Time, or by an IT administrator if you are using a device owned by an employer or educational institution.

- Read this support article If your Apple ID or other options are greyed out in Settings —> If your Apple ID is greyed out in Settings - Apple Support

Tap Settings > Screen Time > Content & Privacy > scroll to Allow Changes.

- If the device is managed (Settings > General > VPN & Device Management), contact the IT department that is doing the managing.