Three things are true:

1. People seek attention, and often lie to get it.
2. Seeking attention is not unique to GenZ. People screamed for attention in Pompeii and Ancient Greece, leaving graffiti on the walls and yelling arguments at strangers
3. Many symptoms of neurodivergence appear at first glance to be typical to the human condition. This is not a coincidence - neurodivergents are human, and therefore face many of the same problems that neurotypical humans do.

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The reason autism and other disorders are evaluated as a spectrum is because the human condition itself is a spectrum of experience. We are not simple creatures.

The reason people are diagnosed with a disorder is often because they have landed somewhere on the spectrum of human experience that involves an abnormal level of difficulty when faced with "normal" challenges.

Simple or routine tasks, time management, emotional regulation, conversation - humans universally face normal challenges in these areas at times, but neurodivergent individuals face greater challenges at higher frequencies, to the point where it can be classified as a "symptom" because it directly interferes with their life in a way that is not statistically normal - it produces unhealthy levels of stress or emotional instability, impairs social and professional engagements, interferes with their ability to reason or achieve their own desires, etc. etc.

These symptoms can often be managed or treated. Just as often, they can only be coped with.

In short, "invisible" symptoms, masking, misdiagnosis, and societal misunderstandings all contribute to this very common idea that the average neurodivergent is just an attention seeker.

Is it likely that you have come across someone who has incorrectly self-diagnosed? Absolutely. People will lie on the internet. People will lie to your face. People will lie to themselves.

But it is also incredibly likely that you have come across people with severe symptoms that you had absolutely no understanding of. People who have been driven to the brink of suicide because they couldn't manage their own mind, people who can convince you they are okay but can't convince themselves.

It's a goddamn spectrum, and people who can't function at all belong on it just as much as people who can mask, treat, or cope with their symptoms enough to blend in. You don't get to write off their existence just because their struggles aren't obvious to you.

neurotypical people still have the same issues neurodivergent people do, just to a much much lesser extent.
Education on neurodivergent people has been hella warped throughout history so it's understandable that you don't have a realistic understanding on the topic.