I can't speak for fairphone 1. But I have had my fairphone 2 for 4.5 years now and I am very happy with software updates.
Is it the case that Fairphone 2 is only on Android 7.1? I understand it's modified, but I don't think we can consider that really supported with updates with an OS that old.
* Major version upgrades ("cookie upgrades") and * Security updates
Fairphone 2 still receives security updates for Android 7 and Android 9 for Fairphone 2 is in beta.