Former breeders may or may not be capable of being pet quality. The bird still needs a home though. A good situation for a former breeding bird may be one in which they are provided good diet and vet care, toys and a nice roomy cage, but are not expected to be a pet. Some may be able to come around to accepting affection from humans, but many are better off with another of their own kind being mostly look at types of pets than ones that want or need physical interaction. It's best if they stay with their original mate if they are compatible and get into a home where they are just accepted, even if they do not progress to being touchable pets. You should never buy a former breeder if your only goal is to make them like you. The goal of buying a former breeder bird, needs to be acceptance of where they are now behaviorally and giving them a good home. Unconditionally.
In many cases, I think they end up going to someone that wants to make them a pet, and when that doesn't happen, they loose their mate and home and enter the rehoming cycle. Many breeders either keep their retired pairs or they rehome them and are very honest. They may rehome the pair and make it very clear that they are likely to be best kept as pretty aviary birds instead of "pets."