The most common kind of dog I see in my area is an adolescent, bought from a breeder as a puppy, raised by newbies or busy young families without any structure, and never taught boundaries. Many were left outside all the time and have no house manners whatsoever. They jump on people, still engage in puppy-mouthing, and they'll just as soon rip up a couch as a chew on a toy....but they're not "bad" dogs...badly behaved, yes, but not genetically defective.
Here's an example that's emblematic of the adolescent problem: we went to the vet for an annual visit for one of our dogs, and the manager at the front desk asked us if we might have room to foster a dog abandoned at the clinic. A client of theirs bought a GSD puppy from a breeder, got in over her head, and "parked" it in play care-boarding at the vet for weeks and sometimes months at a time. The dog was just over a year old and had probably spent half that time in and out of boarding. She periodically got temporarily kicked out of play care for being too rough as she got older. Whenever the owner had her and brought her into the clinic, the dog was totally out of control -- literally pulling down a display wall full of shelving with products for sale! She was ordered to come in through a side door in the future to limit the whirl of destructive, out-of-control energy in the lobby.
They were worried that she seemed to be developing some anxiety living in a kennel, even though let out to play during the day. She had the best vet care money could buy, but she never had a person to bond with, or any meaningful structure. She never learned the word "no." She developed GI issues, had to be put on meds and RX food...and then the next time the owner dropped her off, she told them she was looking for a new home for the dog. Then the owner ghosted the vet clinic -- she wouldn't answer calls, letters, emails or texts for months. She left them several thousand dollars in boarding and vet bills unpaid. After a certain amount of time, the law gives the clinic the right to claim ownership of the dog, which they did. However, she was going to be hard for them to place because she was a little bonkers, and had expensive tummy issues that they feared she would have forever.
She'd been there for several months by the time we met her. We found an inquisitive, confident, energetic dog, desperate for attention. There was nothing really "wrong" with her other than that she'd never been taught to be a good dog.
She spent two weeks leashed to me to keep her from tearing up my house and practice just relaxing on a dog bed next to me. We also started her immediately in our trainer's basic OB course--which she loved because it meant lots and lots of human attention and praise, which is fundamentally all she wanted. She needed to be somebody's dog and have some sort of household job to do.
After just two weeks, I had to pick up an RX refill for one of my dogs and took her with me for a visit, on a prong collar. She walked inside in a nice heel position and sat politely next to me while I paid for it -- totally different dog! Her GI issues had cleared up -- no more meds or RX food, just perfect poops...because she wasn't anxious any more. She was happy as a clam at my house. She loved having a routine. We put her on NiLIF (which she loved, as it meant practicing something she knew how to do).
We also exercised her regularly to drain off the excess energy (DH ran her 3-4 miles every AM, and we walked several more miles in the evening -- that took the frenetic edge off of her and gave us access to a much calmer, more biddable dog that was ready to learn). She loved being a jogging buddy so much that it was probably her favorite part of the day--because it was one-on-one time. People sometimes scoff at the importance of exercise for a young dog, but I think it does for their minds just what it does for ours: regular exercise provides mental clarity and stress-reduction that contributes to good mental health, and I want access to that good frame of mind if we're rehabbing a dog. I can get more done with training when that frenetic, excess energy isn't there. I also think it helped eliminate her anxiety from the boarding kennel. For her, the leash time was also tremendously important as it made her feel connected.
She was with us several months only because we were pretty picky about finding her the right home. She was a lot of dog -- in newbie hands, she'd have reverted to trying to run the house and testing boundaries; in lazy hands, she'd bounce off the walls and tear things up; either way, she would have been returned to the rescue. She needed an experienced owner. We found an active retired guy who'd had 4 GSDs and recently lost his last F to cancer. He loves OB training classes, playing games that are mentally engaging, and walking all over NOLA with her -- she's his hobby, and she's over the moon to be his one-and-only girl and not have to share attention. They're going camping, boating, and spending almost all day, every day together -- she couldn't have a better life.
The problem is there aren't many homes like that. There are way more homes like her first one, that won't put in the time, are too busy doing other things they'd rather do, find reasons not to follow through even if you teach them what to do, etc.
There aren't nearly enough experienced foster homes to help dogs like this either. Had the vet clinic just adopted her out to any well-meaning, loving home, she'd have likely bounced back several times after she tore apart their home. She needed someone to put the time to shape her. There's a tremendous shortage of foster homes willing to do that kind of work.
I passed on at least 6 dogs like her in the past 2 weeks for lack of foster space. That sucks, but there just aren't enough people who will invest the time in these dogs to get them ready for adoption.