...why? SQL has been wildly paradigm-definingly useful for decades. It has driven hundreds of billions, perhaps trillions, of dollars of value. None of this hinges on the ability for an amateur to be able to write a validator for the language. It just seems like such a non-sequitur to me, such a strange thing to call out as a criticism.
SQL hasn't been wildly successful either because of or despite its syntax, it has been wildly successful because organizing data in the relational model and querying it declaratively is extremely powerful. The syntax is just not the interesting part. Any syntax that meets those criteria would do.