adjective
insular
IN-suh-ler/ˈɪnsələr/
Narrow-minded because of limited contact with others.
The insular painting club rejects an unfamiliar approach.

Etymology
Island-related separation came to suggest limited contact, then narrow or prejudiced thinking.
More examples
- An insular outlook keeps them from considering new ideas.
- The department becomes insular after years without outside contact.
Forms
insular
Similar words
- parochial
- Suggests a narrowly local outlook.
- closed-minded
- Emphasizes unwillingness to consider other views.