1) It utterly fails as a coaching tool. "Your framing is 71% correct". Great. Awesome. That's maybe technically correct (the best kind!), but it's utterly unhelpful.
2) It fails at images taken to capture a mood instead of a motif. (Exactly what I'd expect from ML :)
3) It has problems with things that we usually consider iconic photos. Annie Leibovitz's picture of Mick Jagger in an elevator? Meh, 5.2. Dorothea Lange's "Migrant Mother" gets at least a 7.6, so on par with my vacation selfies.
It's a great idea. It needs a lot of love.