Regarding the refrigerator mother theory, autism as a diagnosis has expanded over 100x since that was first debunked and I have no idea why people have any confidence whatsoever that bad parenting cannot cause Autism. This was from a time before people as functional as "Rain Man" were the norm. Twin/Sibling studies were used to debunk this but twin studies don't totally control for shared environmental influences.

It seems more like a politically controversial thing than something which has been seriously scientifically examined either way. It can't be the smoking gun only cause but I see no actual evidence that it's impossible that parental neglect can't be a contributing cause. I will note that it is more politically convenient to simply blame a child's inherent defects instead of parental neglect, since the children relative to their parents lack political power.

I'll also point out that contemporary autism diagnosis relies on parent reports to establish a diagnosis, and people often only get diagnosed if a parent actively seeks out a diagnosis. Autism is also based on observation, if somebody was socially impaired due to neglect, how exactly would an examiner know the difference between that and somebody being socailly impaired due to say epigenetics? I would be rather surprised if who raised somebody doesn't have a rather large impact on if somebody will end up with an autism diagnosis. As in an especially well resourced and attentive parent might mean somebody who would be considered autistic might not be, and somebody who was overstretched and inattentive might have a child who would otherwise not be considered autistic be considered autistic.