"LOL. It's the only formally proven, mathematically correct representation and querying of data sets."
Someone led you down the garden path.
There is absolutely no proof that RDBMS is objectively correct in any meaningful sense whatsoever. Did someone invent an arbitrary standard to measure it by, and then prove that it met that standard? Sure. But that's a far cry from a claim that RDBMS's are somehow "formally proven." That's just pure mathematical silliness and marketing propaganda.
Not that most RDBMS conform to the relational theory 100% (or even 90%), but everything else is mere re-invention of the wheel badly.
As in: "Hey, let's trade ACID, security, uniform access to data by all apps" for cheap speed and ill-thought developer convenience.