There's no atom bomb piece of evidence. There's no line of accusers from over the years that skeevy men in positions of power usually have (Cosby, Weinstein, etc.)
It's one person's word against another's. That's all we have.
Maybe the biggest reason for my reservations about this is that Mia Farrow, after she learned about the affair with Soon-Yi, became all sorts of unhinged. According to Allen, she sent him death threats. She sent him some creepy Valentine with pictures of the kids with needles stabbed into the photo and a heart with a knife through it.
So what you have here is a volcanically livid Mia Farrow over a very f*cked up thing that Allen did (an affair with her adopted daughter) and then this strange, isolated accusation of molesting a 6-year-old on top of that.
I'm a big "innocent until proven guilty" person and there's so much room here for doubt.
That's how I feel about it.