Eh ECS is basically all about making SELECT ... FROM bar, baz WHERE bar.id == baz.id, joins on primary keys, as fast as possible and use it as often as possible. Games are real-time databases with gaudy user interfaces so it stands to reason that posgresql is a game with a bland user interface.
As much as I hate to say Elon might be right... The problem is that critical parts of the US government run on systems older than his goon squad. There's actual COBOL in use, right now today, by the US government.