Then why hasn't this happened over the past 40 years? That's more than one generation of programmers over a whole lot of change from mainframes to PCS, the web,

Then why hasn't this happened over the past 40 years? That's more than one generation of programmers over a whole lot of change from mainframes to PCS, the web, mobile devices and cloud services with thousands of programming languages and tools being invented over that time, but mostly it's incremental process. PLs today aren't radically different than they were in the 60s. It's something visionaries like Alan Kay have repeatedly complained about.