I think that is a gross overstatement. The language has evolved (and should evolve) substantially over the last few decades. Experience from the NoSQL world has influenced SQL (though obviously not always as much as I'd like). I'd also rate the mutual intelligibility of various dialects at around 80-90%, which is still really high, all things considered.
But none of that is the problem. I'm not a data analyst. I don't need a query Swiss army knife. I need a database that behaves predictably under concurrency at a level I can understand. I need primitive operations that map well to the persistence needs of an app serving multiple users at scale. I've never said SQL is incapable or even inadequate at these tasks but figuring out how to do them correctly ends up being a test of English skills rather than picking the right function to call and the right arguments to pass it.
But none of that is the problem. I'm not a data analyst. I don't need a query Swiss army knife. I need a database that behaves predictably under concurrency at a level I can understand. I need primitive operations that map well to the persistence needs of an app serving multiple users at scale. I've never said SQL is incapable or even inadequate at these tasks but figuring out how to do them correctly ends up being a test of English skills rather than picking the right function to call and the right arguments to pass it.