macOS Sierra doesn't have the crispy fonts as they used to be in earlier versions
Tried clearing the Font caches? Kind of an odd issue- I'm not sure if this is gonna help, but worth a try. Maybe it needs and refresher ;) 

defaults -currentHost delete -globalDomain AppleFontSmoothing

sudo atsutil databases -remove and reboot, and maybe it needs and refresher. Its odd since it returns a 3, but maybe something is wrong with your defaults.

Re-pply after rebooting AppleFontSmoothing -int 3 and see if anything first without the string set, you already know that - but let keep the references for others: 

defaults -currentHost write -globalDomain AppleFontSmoothing -int 3