When using Naver or Kakao Map for car navigation, I keep getting rerouted through extremely traffic-dense areas that I don't want to drive through?

I totally understand the frustration. Korean navigation apps love to reroute you constantly. Here's how to deal with it:

Kakao Map (KakaoNavi): Before starting navigation, tap the route options and choose your preference: fastest time, free roads, shortest distance, etc. When it shows 3 route options, manually pick the one that avoids the areas you don't want. If it reroutes mid-drive, you can often ignore the suggestion and keep driving your preferred route. It will eventually recalculate back to your path.

Naver Map: Go to Settings > Navigation > Route preferences to set your defaults. Use the "Frequent Routes" feature to save preferred paths for regular commutes. You can adjust rerouting sensitivity in the navigation settings.

T-Map (recommended alternative): T-Map generally has the best real-time traffic data in Korea. It offers more granular rerouting settings. You can set it to prefer highways, avoid tolls, or stick to main roads. Download it from the App Store or Play Store (free)

General tips: During rush hour, all navigation apps will try to reroute through side streets. If you know the area well, use the nav just for ETA and follow your own route. Waze also works in Korea and some expats prefer its rerouting behavior. For highway driving, all Korean nav apps work well. The rerouting issues are mostly in city driving.