They're not so much "autism speaks" as "we speak FOR the autistic because the autistic can't be trusted to speak for themselves." A more honest name would be "International Karens Inconvenienced by Autistic Children."

In 2013 the APA merged autism and aspergers into the bucket of Autism Spectrum Disorder which many now refer to as just autism. Autism is a spectrum disorder where on one side you have "highly functional" people who are mostly indistinguishable from neurotypical folk and on the other end you have people who cannot speak, cannot function on their own, are dependent on their family or the state their entire lives, and can often have other serious health issues.

Autism speaks was founded in 2005 and merged with groups started in the 90s. So the "Autism" in the name is not really referring to modern ASD as a whole and its focus has always been primarily on the latter group. As a result the group has advocated for things meant to support individuals on the higher severity side of the spectrum, which includes a focus more on family as spokespeople, and supporting research to prevent the worst parts of autism (a "cure"). The "cure" bit is the main issue as in the past that was literally in the mission statement and mentioned in marketing constantly.

The "Autistic community" you encounter online inherently lacks those who can't speak or write. Autism represents an aspect of themselves they each have different feelings about but it's very often a core piece of their identity. As a result Autism Speak's approach is offensive because it takes an objectively more negative view of their identity (a "cure" can border into eugenics in that light) and includes a focus on other people besides the autistic individual. In my opinion, the community is unfortunately highly neglectful of those who literally can't have a voice in the conversation but that's a whole different matter.