I have the same issue with my 16 Pro Max and AirPods 2 Pro.
The only solution for that is turn off Headpfone accommodations
Go to Settings > Accessibility > Audio & Visual > Headphone Accommodations. Turn off Headphone Accommodations.
Remember to put your AirPods into the case once you turn off this option and then you can pull them out
it should help. You should hear announcing incoming calls
I thing it's a bug in IOS 18.1 cause I have my 12 Pro with IOS18.0.1 with this option on and I can hear announcing incoming calls very loud and clear.