Like what
@Shadrach said, if you knew exactly what nutrition they were getting from each food item and what was in it (also that it's not contaminated or starting to harvest bad bacteria) it
may work. Of course, that is a big IF though.
I don't think I'd have the time or even enough leftovers around to do that.
I think doing something like this with healthy safe foods for chickens as enrichment would be great but maybe not a reliable way to feed them.
However, I'd find ensuring all Chickens get equal amounts of each item would be very difficult.
When my hens get a treat, one snatches a big piece, runs off and eats it all to herself. They don't nicely half pieces between themselves
I prefer having our ready nutrient balanced chicken feed there and then feed them additional foods as supplements/treats.
This isn't the worst way I've heard of people feeding chickens though.