I read a quote the other day where somebody suggested that the Clojure ecosystem feels like it’s filled with a bunch of tools from the year 3000, and I think that Crux is a good example of that. It looks very cool.
My personal favourite is the talk from ClojuTRE by the main architect behind Crux, which looks under the hood a lot more and discusses many of the key design trade-offs during initial implementation: https://youtu.be/YjAVsvYGbuU
However, Crux is much easier to justify with stakeholders if you have a complex problem revolving around ad-hoc graph joins or bitemporal queries & audit requirements. Or if you simply have high single-threaded transaction throughput requirements. Postgres in particular doesn't have pleasant answers to this intersection of problems.
I think the tables will inevitably turn against currently-safe choices life Postgres though, as systems like Crux are going to continue to be able to take advantage of the latest and greatest ideas, relatively unencumbered by decades of antiquated design decisions and legacy code. This is where the whole Clojure philosophy really shines in Crux, as all the layers interact through clean and composable Clojure protocols that facilitate new kinds of database modularity. These protocols allow the community to take advantage of whatever wonderful cloud services they might want to use, without any additional ceremony to interact with the core development team.
EDIT: Finally, as new generations of developers emerge the pressure for the industry to standardise on a better relational query language will build. Fingers are crossed for Datalog!