Lost Wi-Fi passwords after reset network settings on iPhone
I came across this question and this was suggested by someone on a forum:


Disable iCloud Keychain from the iCloud settings page (On the top of settings if running iOS 10.3, down the list if running other versions of iOS)
Do the "Reset network settings" to debug the network issue you're experiencing
All the Wi-Fi passwords should now be deleted. What you now have to do is to connect to a network manually, then re enabling your iCloud Keychain, your old WiFi passwords should have resynced and you should now have access to all previously connected WiFis. 


Note that I haven't tested this personally, but I just came across this because I'm trying to debug a problem when my iPad disconnects from WiFi only when streaming Netflix.