Nonsense. The problem domain you dismiss is hideously complicated. Oracle DB and PostgreSQL are entirely different classes of products. No airline runs its reservation system on PostreSQL. That's not a coincidence.
This is also a factor for independent developers (who build airline reservation systems) who need to choose a RDBMS for their product - they'll choose oracle, because ... Oracle can provide support guarantees in a way a Postgres contractor can not.
Which makes Oracle not a different class of product than Postgres, but a different class of support for the product. (which could be considered part of the product, so ... maybe you're right)
What more could we want?
https://medium.freecodecamp.org/the-biggest-codebases-in-his...
Size of software reflects the number of people working on it (and for how long), not essential complexity.