Also keep in mind, the people having problems with anything tend to be the most vocal. Whereas those who are problem free, tend to go about life as usual and are unlikely to post about their lack of problems. So it can create a skewed perception that problems are more widespread than they are.
We fed Canidae for years and were very happy with it. Then the formula switch and our dogs didn't do so well. No digestive problems, but their coats went downhill. So we ended up switching to another food.
I know a few others who had problems with the new food (people I know in real life, not just on the internet) who also switched.
But then I also know probably 8-10 other people (again, in real life) who have had no problems since the formula switch, are still feeding Canidae and their dogs are doing great. Including my mother, several club members, several puppy customers, etc...
So in my little corner of the world, problems with the new formulas did exist, but more people did NOT have problems than did have problems.
At the end of the day, you have to look at your dog and judge for yourself. Every dog is an individual, so no single food works for all dogs. That means sometimes having to experiment with a couple different foods until you hit on the one that works best for your own dog.