I'm 32 yrs old and low donor density. Any suggestions? (photos)

If your doctor (who has examined you in person) says you're not a good candidate for surgery, then you're probably not a good candidate.  One alternative option (which may or may not be in your particular case) would be Scalp MicroPigmentation SMP.  See some before after photos in the video.

In my opinion, your diffuse hair loss is a pattern of genetic hair loss. I don't know why you are averse to starting minoxidil or finasteride. They are probably your best choices. We have used platelet rich plasma to treat your condition. We have noticed an increase in hair thickness as well as a decrease in hair loss.  PRP will have to be continued approximately 3 times per year.Hope this helps. Good luck.

Patients with thin hair are not automatically disqualified as hair transplant patients. If that were the case there would be no HT industry. However, patients with miniaturized donor areas are disqualified. That's what it sounds like you were told by your HT doctor. But this may not be the case. You need to see one or two more experienced HT doctors for an opinion. I have plenty of patients who look as you do on the top in the photos you sent, but still have strong donor areas. We use that donor area to strengthen the hairline and frontal third area to frame the face and it works like a charm.