As I sometimes say: everyone is on the spectrum. I just think the boundary between what was considered 'normal' and what was labelled as some kind of condition has moved significantly. Back along, autistic meant Rain Man like, nowadays it's mode widely recognised with much milder symptoms.
My uncle was almost certainly autistic, but was never diagnosed because it just wouldn't have been recognised back then. And if it had been, he'd have been bundled away to a facility. So my grandmother would never even consider that he had issues, despite it being perfectly clear that he would never be able to live independently.
More recently my friend's ds (currently teenage) has been diagnosed as autistic since about age 6. He certainly had some nd behaviours at primary age, but these days he's completely grown out of those and most of his issues appear to be behavioural than anything else. He's certainly way more sociably competent than I was as a teenager (and I don't consider myself to be nd). There's no shyness, awkwardness or lack of self confidence that many autistic people display. I genuinely doubt he'd get newly diagnosed as autistic if he were assessed today. But he has the label for life, for good or bad.
His younger sibling is awaiting diagnosis for ADHD. His issues are much more pronounced, and escalating as he approaches his teenage years. But again, I think a lot of it is diet and behaviour led - he's regularly pumped full of Coca-Cola and sugary sweets (right before meal time too, but his inability to then sit at the table and consume a proper meal is put down to adhd). They both talk to and about people in a deliberately horrible way (proven since they can also be really nice and polite when it's in their interests to do so), but they're never called out on it or disciplined for their words or actions ("it's because of his autism" or "I need to pick my battles with him").
I do think autism is very over diagnosed these days. I think a lot of parents push for a diagnosis for any kind behaviour that seems a bit off - they want something that explains why their DC is doing (or not doing) something they can't fully understand. And I think a lot of people grow right out of the childhood autistic traits in adulthood. Some people will say it's because they've learnt to mask their symptoms, which is likely true of some genuinely autistic adults. But is also overused as an explanation for people who were never really autistic in the first place.
It's also overused to excuse bad behaviour (autistic or not). At my DC's secondary school there are a lot of kids with Nd, learning difficulties and behavioural issues. The school prides itself on taking these kids (cynic in me thinks it's primarily for any extra funding that might come with it), and there are quite high poverty rates around here, so a lot of kids with behavioural issues (many of whom have been given a badge/diagnosis to explain it, rather than being put down to a lack of discipline or poor parenting). But my own dc notice day in day out that these kids get special treatment - completely let off for things that other kids would get in trouble for or if there's an issue between an Nd child and a nt child, the NT child is always the one who takes the rap for it.
We want Nd people to be fully integrated with the rest of society, but I don't think we're preparing them as children for adulthood or independent living properly. It seems all through childhood they're taught that their diagnosis is their excuse. That's not going to cut it as an adult - I expect a lot of young adult offenders had (or would have been given) a diagnosis of being nd as a child. We need to be trying to teach them better self awareness, and responsibility wherever possible.
Sorry, that got really long!