That’s pretty standard at a large practice. It allows their doctors to have predictable schedules. They will probably rotate you through many doctors and midwives to increase the likelihood that you have met the person who delivers your baby. I didn’t like being rotated, and unfortunately I hadn’t met the person who delivered my first, but it was fine. For my second pregnancy I looked for a solo practitioner, but had a hard time finding one who was taking new patients and took my insurance. I ended up staying at my old OB practice because it was convenient. It was more important to me to have consistent prenatal care, so I found a practitioner I liked and saw her exclusively, refusing to be rotated. She did not deliver my second baby - again, total stranger did - but it was fine.
If it is really important to you to have someone you know there, consider hiring a doula to be your support person.