If you talk to those who have been in the breed for 20+ years the general consensus is that the AB is a mere fraction of the dog that it once was. I would give anything to have a classic dog from way back when.
I won't pretend to have the knowledge of people who have worked with the breed for many years, but I did do a lot of research before buying my AB two years ago. The more I studied the breed, the more I found myself attracted to the original Standard type. And when I studied the Standard type, I learned that the Old Southern White bulldog, sometimes called the White English, was the foundation for that strain.
I found only a few kennels still breeding the Old Southern White lines:
Laura Kennels and Joshua Kennels share each other's dogs in their breeding programs. Both these breeders are serious about health, temperament and working ability. Another fellow who has a lot of knowledge to share about the Old Southern Whites is Ralph Citarella at White Knight.
People sometimes don't understand what a dog breed was intended for. They decide they like the look of a dog, so get it and then try to make it do a task. Often, the dog wasn't bred for that task. So breeders start to change the dogs to suit consumer demand. That is what's been happening to the AB, and it's ruining the breed.
Old Southern White bulldogs were used over many generations to hunt wild pigs and boar, catch and hold livestock, and drive cattle. A dog hot on the scent of a wild boar isn't supposed to bark because that will tip off the boar. They were bred to be quiet dogs. But people wanting to use ABs for protection work will often complain that they can't get their dog to bark!
Working bulldogs sometimes get gored by a wild hog and need to be stitched up out in the field- without anesthesia. If you're a hunter and come across a dog that needs your help, you don't want that dog to bite you when you start to work on it. You need that dog to be able to restrain its natural instinct to bite when it's in pain. So bulldogs that remained calm and didn't bite while under stress were considered good dogs and got bred. Bulldogs that "lost their cool" and bit people were not bred.
Cut to today, when more and more people want ABs for protection and bite work because the AB looks like an imposing dog. Trying to make bulldogs bark and do bite work is the opposite of what they were originally bred for. I'm not saying it can't be done and done well, but a lot of these dogs just don't have the temperament for that kind of work. So breeders are changing the dog to suit the public's demand, and messing it up considerably, IMHO.
As a result, we're seeing more and more American Bulldogs that are dog-aggressive and have dominance problems in the home. They're often hugely oversized and muscular, to the detriment of their structure, breathing and endurance.
If you want a classic AB in all of its original glory, the Old Southern Whites are still around. You just have to look a little harder to find them. Mine is sleeping on my feet...