I'm an older Millennial. Autism was not a word we used when I was young. As a young parent I had autism described as a very specific set of negative behaviors, because autism was defined by the problems it caused (same as ADHD). But that's not accurate.
A lot of neurodivergence isn't what people picture when you say autism or ADHD. A lot of the behaviors and experiences that people picture are neurodivergence under extreme stress. It's like defining hunger as being near death because of starvation.