While you might not have achieved the exact density you hoped for, overall, the change from your before and after photos to me look dramatically different.
Dr. Soni recently recommended 4,000 grafts (FUT+FUE) for me. When I inquired how many hairs that equated to, I was told between 7,500-8,000, therefore your transplant being 4,500 grafts probably equated to ~8,500-9,000 hairs. I am new to the hair restoration world, but given your level of hair loss, I would think a few more hairs (correct me if I am wrong) would be needed for full coverage with density which I am guessing could be accomplished in another procedure.
I know that the illusion of density also depends a lot on hair type (fine, coarse, curly, etc.) so perhaps that may be a contributing factor.
Overall, it looks solid to me, but maybe my expectations are not high enough