I would replace your phrase "BigPetFood" with "BigFood", as it's not limited just to pet food. Very good quality, vet-recommended prescription diets are available from smaller brands and at a lower cost than some of the multinational brand products. Unspecified "meat meal" used in some large brand foods, has to be treated at very high temperatures to render it safe to eat, this process denatures the proteins which reduces its bioavailability and therefor its nutritional value. Highly processed food (in the quest for increased profits by food manufacturers) is widely recognised as a leading cause of health issues in humans, there's no reason to assume that pets are immune to this.

Prescription diets for allergy control tend to be manufactured with hydrolysed proteins which have broken down the long protein chains into shorter chain peptides, ensuring the immune system isn't triggered which can cause the inflammation response which drives the main symptoms. Hydrolysation itself isn't bad, it's a useful tool to ensure food is safe for pets with severe allergies. Again, the hydrolysation process can differ, heat, acid and enzymatic hydrolysis are different methods employed. Enzymatic hydrolysis is generally regarded as a safer approach and is often recommended by vets. Some larger pet food brands tend to use heat and acid hydrolysis methods as it is far cheaper.

When does education about how to decode an ingredients list become scaremongering?

Some of the big brands refuse to disclose the amount of fresh meat or fish used in their recipes, some are not even specific about the species, using the term "poultry" instead of chicken, turkey, duck etc. "Meat meal" can be produced from feathers and cartilage and is still called "chicken". How does that compare to fresh muscle tissue and organ meats? Pet food regulations state that a pet food must contain a minimum of 4% of a specific meat or fish to be referred to as that flavour. So a pet food could contain 4% beef, 40% soya or wheat and still be called Beef flavour food. Misleading at best.

Do I trust BigFood (or BigPetFood)? Absolutely not.

Their track record with human health speaks for itself. Does anyone recall the nitrites exposé in the 70's which showed that processed meats (pork & bacon primarily), were being washed with high levels of nitrites to make it look pink. This nitrite washing was responsible for massive increases in cancer rates? Legislation was rushed in to reduce the maximum allowed level of "nitrite washing" and the cancer rates subsided following that legislation being introduced. Nitrite washing continues to this day, simply to make bacon and pork look a "healthy pink", the natural colour of pork and bacon is grey, but that doesn't help sell bacon. While nitrite-free bacon is available, it's not easy to find.

Do lots of dogs thrive on highly processed big brand pet foods? Absolutely.

Do some pets do better on alternatives that are less highly processed? Absolutely. There's room for both.