This is pretty much my philosophy as well. I use flock raiser as my base but don't worry about it being diluted by food waste, grasses, weeds, insects, etc. I think fresh food is not only good from a nutritional stand point, I think that it helps with the mental health of the chicken as well. They like to forage, scratch and work over larger food items like squashes. I also value the reduction of food waste.I believe that commercial all-flock of at least 18% protein is my best insurance of good nutrition, but I also believe in the value of offering green stuff and a good variety of options. I value the chickens' ability to reduce household waste by consuming the trimmings from meal prep and the leftovers that get shoved to the back of the fridge and forgotten
This whole thread has been very interesting. My two cents is that I suspect that there is quite a bit of variation across chickens for what is an adequate, much less, optimal diet for them. Chickens are descended from breeds that evolved all across the globe and even now are kept in different environments for different purposes. Although I am pretty confident that feed companies have come up with the cheapest feed recipes possible for keeping a commercial layer in acceptable health for 2 years, I am less confident that this works as well for dual purpose birds, hens that go broody, roosters, etc.
I've always assumed I could make homemade feed that is better then the "bare minimum for good health" that is in the commercial feed, but to be honest, that would require a level of sourcing ingredients, expense and work that I haven't been willing to undertake. So I give them commercial feed and liberally supplement through forage, yard waste and scraps.
I think of it this way. I'm sure if it were possible to study accurately (and thankfully it is not) I'm sure there is a generic diet that would be considered adquate for most humans and a way to make that diet using the least expensive ingredients possible. Although I would gratefully accept such a ration in lieu of starvation -- or in lieu of a grossly deficient diet -- I am happy to take my chances with a varied diet. I also think that there is tremendous variability amongst humans as to what is a good or workable diet. Some people thrive on veganism, others keto. Some do poorly with gluten. Some people even seem to do OK eating fast food as a staple. I can't imagine chickens are so very different.