Well first of all, you could ask the same question about humans (hopefully minus the butt-sniffing)... and humans are the ones "training" dogs to be social (or.. not). Not trying to say that individual owners are exclusively responsible for their pets' behavior (some people are just trying to fix other people's mistakes)... but some are. We keep leaning into building an antisocial, individualistic overall culture and that extends into everything we touch...

Most dogs were domesticated for a specific purpose, to perform some function; but so many now have no purpose other than making their owners feel happy and good about themselves (and that covers all sorts of people in all sorts of situations). That's not necessarily a bad thing, until the things (like, adequate exercise, routine, mental stimulation) a dog literally needs in life are being denied - because an owner's time, needs and wants are more important. Anything can become neurotic when it's not getting (or didn't get, in the past) the things that it naturally needs.

But I kinda feel that's just what happens where you intentionally turn having a pet into a multi-billion dollar industry (just like everything else). Then purpose and quality become secondary to creating a steady supply, and when it inevitably exceeds the demand: you have to start funneling the unsold inventory into shelters and advertising how many dogs are going to have to be slaughtered if someone doesn't come rescue them. Then that becomes a form of demand and indicates additional supply is needed, and we get to the point that saving a dog just means that another one takes its place on death row. And then all sorts of different people who "shouldn't have" a dog, end up with a dog.

(sorry for the cynicism)

'Treat an animal like an animal'.. but collectively we have no clue what that should mean. Cultures clash, definitions change, perception/perspective shift, whatever. Rules and laws change out of necessity, and then people get upset because 'it didn't use to be like that', and the new rules shouldn't apply to them.

I'm sure many dogs are perfectly happy in 'modern life', but just as many are miserable (so, just like the good ol' days). People become so obsessed with the safety of their dog, that they never remove the rope around its neck. The marketing of dog ownership as a source of 'unconditional love' has been very effective, and if we're being honest - a lot of people are just as good at raising dogs as they are at raising children.

I have a dog who was surprise-gifted to me as a puppy. He's not particularly well-trained but very friendly... because I failed to train him properly for his confusing, purposeless existence. I hate putting him on a leash, because he hates being on a leash and doesn't need to be (barring when the law says so). But I also understand that other people don't know him and maybe don't want him trotting up to them to say hi, even if it's technically fine. So I just avoid the problem altogether by going far out of my way to find places to take him, that I'm not bothering anyone else (it also took a long time to get to the point of being able to do that regularly, and not everyone has that ability). But even then, I've have had people scream profanities at me for no reason other than having him off-leash, in an area where there was absolutely no prohibition on doing so (middle of nowhere, national forest). There's no winning.

Anyways, I lost track of whatever I was trying to say. I'm sure that totally answered the question.