The term "spectrum" leads to any kid who is slightly eccentric to be labeled autistic, any kid who is a disciplinary problem to be diagnosed as ADHD, and so on.
For a set of behavior patterns to be meaningfully defined as mental illness, the behaviors have to interfere with a person's ability to function. Simply having some characteristics in common with a mental illness doesn't make one mentally ill. Someone who checks to make sure that his stove is turned off twice rather than once doesn't have obsessive-compulsive disorder, the guy who needs to do it so many times that he won't leave the house really does have a serious condition that requires treatment. Similarly, the nerdy kid obsessed with dinosaurs or model trains isn't autistic - the kid who can barely speak and spends all day rocking back and forth is autistic.
The worst part of it is that perfectly normal but rambunctious kids who just need some discipline at school or at home are diagnosed as ADHD and medicated with ritalin.
So true. There are some real cases, but in most cases, there's nothing wrong with the kids. Starting in the 2000s, more and more kids were diagnosed as "on the spectrum" or labeled with ADD/ADHD or some other new disorder. So many kids were being medicated that they were sometimes called Generation Rx.