Ok but XTDB has a lot in common with Datomic and is open source but still hardly widely used. I think this is partly because most people don't consider 'temporality' as a feature a database should offer; rather, they believe temporal problems should be solved via proper schema design and application logic. Additionally, using datalog (or any esoteric query language that isn't SQL) locks you out of many battle-tested tools that enterprises rely on.
The XTDB team has pivoted towards a SQL-first approach (though still supports datalog) and now 'only' has the 'But why not just use Postgres' problem to solve.
Having personally moved from trying to use Postgres for everything (including lots of timeseries data with Timescale) to a dedicated and relatively unknown DB built purely for the purpose I want it for (QuestDB), I am all for more people trying to build databases that do specific things better than Postgres. However, it will be very difficult to create something that does literally everything Postgres can do but better, which probably makes Postgres the sensible choice for the majority of applications.