Of course, in reality disinformation goes through many channels on facebook, but (my understanding is) a ton of it is organically shared and commented material and links. I.e. a different kind of content from ads altogether.So facebook ads could still be ineffective, yet disinformation campaigns highly effective.
I'd also discount the studies on fake news from Spring 2017. The game has changed significantly since then.
My impression is a bit different from "criti-hype": I think Facebook is likely extremely good at promoting engagement, pulling attention, and changing minds -- HOWEVER -- FB has very little control over what content is able to be successful in this environment they've created. It takes an entire web ecosystem (quasi-news sites to host 'articles', etc etc) to conduct these disinformation campaigns and they have to resonate with people organically interacting, not just popping up in ads.
The fact that FB can't at-will divert all this attention onto breakfast cereal or brake fluid or whatever doesn't mean the disinformation is ineffective in the political sphere.
Edit: it's one thing to build an extremely fertile petri dish, it's another to control which organisms end up colonizing it.