I'm still looking for a new OB myself. But, a low number of ultrasounds is definitely not a good way to judge a doctor. In fact, that's just good science. You shouldn't have any ultrasounds beyond what is medically necessary and 23 weeks is a normal time to find out the sex of the baby. There has been no comprehensive study of how ultrasounds effect fetuses, and then our babies, in the long term. In fact, there is some speculation - but I emphasize no proof yet, that the increase in ultrasounds is one of the causes of more autism cases. Many ultrasound experts and OBs strongly recommend against ANY novelty/keepsake ultrasounds as well. A great doctor is one that keeps up on the latest research, cares for their patient, and only performs tests & interventions when necessary.
There may be other reasons why you'd like a new OB, but that really shouldn't be your main criteria. Hope you find someone that works for you.