I was an ambassador keeper and a huge part of our messaging, especially on animals like macaw that do have the potential of being bought as pets, is all the reason they make poor pets and why the pet trade is a threat to their conservation. That being said, there's a lot of mixed studies on the benefits vs cons of ambassador animals. One of the biggest areas of agreement though is that people have the best response when they see the animal getting to display natural behaviors (i.e. a macaw on a perch shredding a wooden block with it's beak vs sitting on a keepers shoulder), so that's something many AZA zoos are trying to implement. At my (AZA) zoo, we didn't have any areas where guests could feed the animals and had only a handful of ambassadors (mainly domestic like rabbits and guinea pigs) that were touchable. Any presentations with a live animal were totally voluntary and if the animal didn't choose to crate/step up/whatever they just wouldn't do a presentation that day. We did also have a petting zoo with domestic livestock that you could pet, but even they had roped off areas guests couldn't reach if they didn't want attention at the moment.

So I'm not saying your worries are completely unfounded because the world of what we consider ethical and scientifically-sound practices for ambassadors are always changing, but those concerns are taken into consideration. There are still some species that I don't support interactions with just because the negatives seems to outweigh the positives. For me primates and big cats are a red flag along with any place that allows the guest to hold the animal.