This is a pretty major issue that would break countless contraptions that have observers in them. Confirmed the bug acts like this in my snapshot test world.
I have confirmed from my own experiments that villagers do not detect doors.
In villages.dat in the nether, end, and overworld, not a single village is created. Villagers do not track towards doors, do not breed, and do not produce iron golems.
Stephen Spohn
This is a pretty major issue that would break countless contraptions that have observers in them. Confirmed the bug acts like this in my snapshot test world.