OK, I must have the only decent Petco near me. While it's true some of the associates are ignorant and probably couldn't give accurate advice on raising a cockroach, I have gotten some really good and really accurate advice from others. They have a care sheet for everything they sell and most of them are almost identical to the care sheets I've seen on the web pages of the very experienced people in this forum.
At the Petco near me species are always kept separate and are never mixed. There never seems to be overcrowding. There are never any sick looking or dead animals on display, in any department. Their displays are not, for obvious reasons, as elaborate or "natural" as ours in our homes, but the animals have what they need to live and appear to be healthy. I have bought several living things from them and have had them for a while now, with no deaths to report.
I know there are a lot of really bad pet stores out there, but there are some good ones, too. I think a lot depends on the management of individual stores. Maybe it's not fair to always bash ALL PET STORES. By the way, there are also a lot of really bad breeders out there.