ID in settings is greyed out

So, you can try to go in: Settings > Screen Time > Content & Privacy > scroll to Allow Changes, then check if Account changes are set to "Allowed". if not then set it to "Allowed", wait a moment and check if it continues to be greyed.

Let me now if it fixed your problem.

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 document about using Screen Time on an iPhone, iPad, or iPod touch --> Use Screen Time on your iPhone, iPad, or iPod touch - 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.