I would only make a closed-source solution a centerpiece of my business if:
* The thing is known to work for a number of other people, and uniquely solves my urgent problem, while no open solution can't do anything comparable. This is probably the Datomic niche.
* The thing was around for ages, and is a cash cow of a major and reliable software maker, and is also significantly better than open software in some important area. This is how MS or IBM sell their databases; Datomic doesn't have nearly enough mindshare to compete here.
* I'm hastily building an MVP that I plan to scrap anyway when the growth hits / the startup is acquired. Datomic is likely too expensive for that.
By necessity, the first case holds for a small number of businesses.
It's not helping clojure grow as much as it could though and it's a bit a chicken/egg problem, more clojure users could be more datomic users and vis-versa.