That's surprisingly terrible. Unbelievable. To think that Google can't even support its own devices after 3 years whilst the Linux ecosystem supports a silly number of devices and platforms, substantially on a volunteer basis
This is terrible. I too have this phone and it still works perfectly, no repairs have been required. Are we now supposed to buy a new phone every year? Every two years? This is getting absurd.
Also, Windows at least tells you that support for your version is coming to an end. Google/Android has not notified me in any way that my device is not being supported anymore, that new updates will not be coming, what that might mean for me and what they suggest I should do.
I'm running Cyanogenmod on the Nexus 5 with dec/16 patchlevel. It comes as a minimal base over which you can install whatever apps you want. You can also install LineageOS or Sailfish OS. This is better than the level of support Google provides.