Job ads have been historically marketed to only certain sectors of our society - white, educated and tech-savvy individuals. To increase diversity of job applicants, employers should be required to post their jobs on numerous sites including sites that cater to different ethnicities, languages, etc. If you're looking for diverse job applicants, you'll need to share beyond the average job ad platforms.
When I worked for a city government the HR manager said she would only post jobs through the city's website and not include wide-sharing platforms like Indeed. I believe this will lead to a narrow applicant pool and you'll miss out on interested and qualified employees.