Dentist Website Won't Rank

Background: I run an seo agency and have been tasked with ranking for the keyword dentist "city". I can’t get past the 2nd page for my life. We have grown the GMB to have the most reviews as well as the highest reviews for dentist in the city. The home page has better / more backlinks now than those on the first page ever had. In addition, I believe the home page is much better optimized than others on the page. Why won't my ranking change? It makes no sense. The only thing I can think is that because its a larger dental office, the small GMB profiles have the advantage of having "DDS" / "Dental" / "Dentistry" in their GMB name. Any thoughts are appreciated. Thank you