For all practical purposes, breed "improvement" in conformation means to increase "typiness" of a breed, or the traits that make it distinct from other breeds. It also means to increase uniformity, because how could a breed be defined by multiple types?
In some breeds, the distinctive traits are obvious to all from the day the breed is recognized by the AKC. The wrinkly face of a Neapolitan Mastiff was immediately seen as a trait that needed "improvement", i.e., exaggeration, hence the grotesque sorry animals you see in conformation. There are many, many examples of breeds where you could have easily guessed the direction it would go in the ring: The long, flowing coat of an Afghan hound, the progressively longer bodies and shorter legs of dachshunds, corgis, and basset hounds, etc.
Breeds that start their conformation history without some obvious traits to increase "typiness" take unpredictable paths. These are the breeds that start with fairly normal body proportions, a short or medium-length coat of unremarkable color, and a normal dog head. In some cases, it may take quite some time before there is a gelling of opinion among the show dog world about what makes the dog distinctive. Before "type" becomes well-defined in judges's minds, the breed champions may vary widely in appearance, but will rarely look exaggerated in any particular trait. Once opinion gels around a set of traits, show breeders set out in earnest to produce more and more distinctive dogs.
The paths that breeds take or don't take are often (to me) surprising. Collies and shelties are closely related breeds. Sheltie breeders often hate the term "miniature collie" but shelties descended in large part from collies. In the breed ring, coat has been exaggerated in a similar manner (excluding smooth collies), but head shapes took a very different path. For some weird reason, it was decided that collies should have a wedge-shaped head with no stop, but shelties have a distinct stop. Even more bizarre is the egg-shaped head of a bull-terrier, which I would never have guessed would be the chosen path for that breed or ANY breed. (How could anyone consider that head to be desirable?)
Goldens were originally considered a variety of flat-coated retriever, yet the ideal ring flat coat is leggier, while the ring goldens have gotten longer-bodied, shorter legged, and have a head with an increasingly dome-shaped, puppyish look. Current genetic studies indicate goldens and labs are closely related (probably, there was quite a bit of genetic exchange before the stud books were closed, and probably afterwards as well). Both are water retrievers with similar functions. Yet, the show-ring lab abruptly took a turn down the path of looking more and more otter-like, not just in the tail, but in the whole appearance. There's nothing wrong with an otter being round, fat, and short legged. It's a standard morphology for aquatic mammals. The conformation folks seem to have forgotten that the function of a lab is not actually to catch fish and that labs spend a much greater proportion of their life on land than an otter does.
However, all of this discussion about the lab BOB at Westminster has totally overlooked the biggest problem with the show ring: that looking at a dog trot around a ring tells you virtually nothing about that dog. What if every dog in the conformation ring looked like a field trial champion? Judging them would still be like a building inspector being required to do his inspection entirely by looking at the building from the outside. He could tell if the building had walls perpendicular to the ground, and he could see the color of the walls, but that would be it. He wouldn't be able to determine whether the plumbing and heating even existed, much less whether they worked properly.
Similarly, a conformation judge cannot tell whether a dog has good vision or hearing, whether it can remember a mark, whether it has a soft mouth, whether it has an "eye" for sheep, whether it can course a hare, etc. The judge can't really judge ANY of the most critical traits that make a retriever a retriever, a sheepdog a sheepdog, or a saluki a saluki. It's a terrible way to judge dogs.