Dog food bags are tools of pet food companies who want you to buy more pet food!
I had a vet tell me the exact same thing a few months back.
We currently feed our dogs Nature's Recipe, with Helena getting the large breed puppy recipe. They get a cup each in the morning and evening, along with chopped up veggies - carrots, string beans, cabbage, etc.
If we go on an adventure on the weekend, I'll give her a small mid day meal. Rupert is still on a diet, so none for him.
The nice thing about the vegetables is that we never throw out rotten produce anymore. Plus they have a 'seconds' area in the produce section at our supermarket. Stuff that's marked down as it's not up to their usual quality, but fine for a dog.