Oh... where are they then? These billions of escaped chickens you seem to think are running around somewhere?
I thought it was fairly obvious that "in all this time" meant over the last 4000 - 6000 years or so of recorded history. Most of those chickens are dead. Old age, if nothing else...
The one place NONE of them are is directly overhead, at an altitude of 200' or more above ground level. THAT is the thing which cannot re-evolve.
Likewise you can play with the genetics and produce a chicken with teeth. What you won't manage to produce is a chicken which can kill and eat prey animals WITH those teeth. THAT, and flying 200' above the ground, are examples of what I mean by complex traits.
Wendy for something to be obvious it must also make sense.
But that is neither here nor there, since several posters (myself included) have provided for you demonstrated examples of evolutionary innovation where new capacities evolved that did not previously exist. From tricolor vision in primates to evolved lizards on an island to (yes) examples of flying chickens... these are not theoretical occurrences.
We can demonstrate these occurrences, so there is little need to wring hands over your chickens... that argument has already been mooted by the actual evidence.