I have been searching, trying to find someone else complaining of the same problem.
Here is what I have noticed. I have a 2023 MX. I have an iPhone 14 pro. If I make phone calls using FaceTime audio the call quality is actually pretty good. If I make a phone call using the regular phone network, the microphone on the Tesla is terrible and the people on the other side, have a very difficult time hearing me.
A good test is to open up a voice note and try recording as you drive. You will see the quality is actually not that bad. This seems to be some sort of software issue between the iPhone and the Tesla if I am correct.