My views, while informed, are my own and other psychologists will likely have a different view on one or more of these points. So here are a few points that I would like to make:

1) "On the Spectrum", depending on who is saying it can mean autism or it can mean, has autistic tendencies or traits. Recently there was a change to terminology that grouped 3 different diagnoses (Autism, Aspergers, And Pervasive Development Disorder) into one diagnosis (Autism Spectrum Disorder). If a professional who has assessed a child indicates that they are 'on the spectrum' they likely mean they are diagnosing Autism Spectrum Disorder. If it is anybody else, they may feel that the child has Autism, but being diagnosed with autism requires having more than just traits, because in reality, pretty much everyone I've ever met has at least one trait of ASD.

2) In many cases parents are relieved at hearing the diagnosis for several reasons. Including access to interventions, (early intervention makes a big difference in life outcomes for those with ASD), closure (knowing that what they saw all along was right), and being able to develop a plan for their child.

3) Some of the most difficult cases have been when parents are told that their child does not have ASD when they believed it.

4) We still don't know what causes ASD (the many roads lead to Rome theory is widely accepted), but recent research (last 5-10 years) has shown that trauma that occurs in the early years can cause PTSD which looks a lot like ASD, so likely many children being diagnosed with ASD actually have PTSD. Sometimes it isn't possible to know if the trauma occurred because of ASD or if the ASD symptoms developed alongside the PTSD or some other combination as children with developmental disabilities are abused (all types) at much higher rates than those that do not. If you want to learn more, I recommend looking into Toxic Stress.

5) Kids do seem to be different today than they were. Much of this can be attributed to changes in parenting and the society we've created trying to 'protect' our kids. For example we're excited that we can leave our now 12-year old daughter home alone for a few hours without concern that CAS (our Child Protection Agency) will be called on us. As a kid, I came home to an empty house from school at 8 or 9. Today there is less time playing outside, less opportunities for unstructured socializing (our kids classes even play movies during lunch time because it keeps the kids quieter while they eat). This isn't how we want to raise our kids, but our complaints fall on deaf ears, and when we try to teach our kids responsibility, those who mean well, short circuit the efforts of those with training and who know the research (we've had CAS called on us for example).

6) For most of the diagnoses (if using DSM-V) there is a key requirement. The issues have to be causing clinically significant problems in current functioning in one or more important areas of their life. You could theoretically have all of the symptoms, but not be diagnosed if you are still functioning well.