I work at a Petsmart in Florida.
I agree...not all Petsmarts are the same. Not all pet stores are the same. That is true for all. I have dealt with bad mom and pop stores as much as I have big box ones.
The key is educating yourself. Often times, I will go to a pet store and start asking an employee about an animal that I am already knowledgeable one. Ask them common and uncommon ones. If they are lying or just making stuff up, I call them on it, and have even reported them to their managers and corporate. There is NO excuse for poor training when it comes to the lives of animals.
My Petsmart is great honestly. Many of the people in petcare have many of those pets themselves. And/or have worked at the store for years and become very educated about the husbandry of many of the animals they sell. I have seen my Petsmart mix up the food a bit. They give them everything from fresh greens and veggies, to freeze dried, to pellets, to crickets and waxworms. Keeping their diet varied. Not all pet stores do. Also when you purchase ANY pet, you can ask for the feeding chart they have been using. If they don't have one, reconsider purchasing it. Pet stores should keep record about the eating habits of their animals.
I have also bought dragons from Petco and Petsmarts. I bought one from my Petsmart a couple of months ago. She is very healthy, leatherback with some amazing red markings.
Understand though, when it comes to big box, they get most their animals from "mills". Least their mammals. Many small pets were inbred. Reptile-wise, I have no idea how good or bad the dealers are. In the Petsmart I work at, it is rare for us to receive a sick reptile. From what the managers told me, unlike the mammals and birds, the reptiles generally come from breeders, who sell wholesale to dealers, and then to Petsmart/Petco/Pet Supermarket.