I hear this claim made repeatedly, that ABA is ‘a science which is proven to markedly improve the lives of people with autism and of course, their families.’

It’s just not true.

Most people are not aware of just how poor the evidence for the effectiveness of ABA really is. Most of the claims are based on a paper written in 1987, in which almost half of the 19 children who had 40 hours of ABA and aversives (shouting loudly at them, slapping them) were said to go on to mainstream school without support. They were described as ‘recovered’. No other study has replicated those results. The science behind ABA is really very flimsy.
I wrote a bit more about it here.
For a thorough investigation of the science and ethics behind ABA (or rather the lack of both), you can’t beat Michelle Dawson.