I don't exactly get this argument. It is not only about what you see on screen, I was talking about geographic operations like spatial queries being executed on the globe rather than on a projected 2d surface.
But it's perfectly possible to create geodesically-correct buffers, for example - such as you might see when calculating ballistic missile range over thousands of kilometres - in a 2D projection, and indeed this has been available for decades. And we have plenty of global models, such as WGS 84: https://en.wikipedia.org/wiki/World_Geodetic_System
So what exactly are you talking about?