Let's be bluntly, even brutally, honest with ourselves. I have met parents who did as much as my own parents, from physical therapies to demanding the schools do better to meet my needs. These parents have spared no amount of time or effort to help their children, often sacrificing dual incomes to have one parent at home full-time.
And yet, for all their efforts, there is negligible improvement, beyond what might be expected as an autistic child ages. Yes, improvement, but not enough to live independently or to have the types of social connections the parents envisioned.
You can spend all the time and energy humanly possible on the "recovery" of your autistic child and not achieve the desired result. By contrast, I have met autistic adults who were institutionalized, abused, dumped into foster care, and despite everything these autistic individuals have emerged as engineers, scientists, professors, and generally "successful" adults.
I'm sure that's not what any family wants to read or hear, but sometimes you cannot predict how the environment and nurturing (or lack thereof) of a child will affect development. Sometimes, the parents provide that extra bit of support to help an autistic child become an independent adult.
My parents did more than I could ever repay, especially during the first two or three years of my life. I was born with a severe diagnosis, and it would have been easy for my parents to surrender to the fate doctors declared at birth. At the same time, there was random chance involved in my progress.
My parents, working their entire careers with disabled adults and children, know too well that "miracles" are rare, even in the best of situations.
It's hard to admit fate, luck, or chance has anything to do with life, but that's actually a large part of existence, in my experience. You have to prepare for the opportunities that might come along, but even the best people making the most effort can end up in lousy situations.
There's no doubt my parents influenced my attitudes and choices. It's also inescapable that my wife has provided the support that allows me write each day. Without my wife and parents, I'm not sure what would have happened to me.
Being able to write is fortunate. My injuries at birth could have easily left me unable to write or even comprehend words. It was both bad and good luck, random chance, that produced me. My duty is to make the best of what I am capable of doing. That's what my parents taught me.
You cannot feel guilty about a child's physical limitations. My parents have nothing to do with my paralysis, my brain trauma, or any other physical condition. My family did all they could to help me make the most of my life, despite limitations beyond their control.
If you're a parent, don't dwell on why your child is disabled. Your child needs you to love him or her as-is. Focus on the present and the future. Guilt just weighs you down.
And please, don't pay too much attention to parents implying you don't do enough for your child. Only you know how much you do or don't do. There are human limits of what any parent can do and provide for a child.