AFAIK, albeit it was initially based on the ideas implemented in Om.Next, modern versions of Fulcro are very different today.
I think Om.Next was just a collection of a few, rather conceptual, abstract objectives, quite experimental (perhaps even ahead of their time) and untested in production.
Too bad that Cognitect couldn't give David Nolen a carte-blanche and let him work on it 100% of his work time.
I'd rather live in a world where libraries like Om.Next become popular, and not stuff like Angular.
ps.: I used Angular. And I loved it. Angular made sense. Sometime around 2009-2010. But it stopped making sense. And I stopped liking it. You still can build awesome things with it, and people still do. And I still don't like it.