> Modern text editors have higher latency than 42-year-old Emacs. Text editors! What can be simpler? On each keystroke, all you have to do is update a tiny rectangular region and modern text editors can’t do that in 16ms. It’s a lot of time. A LOT. A 3D game can fill the whole screen with hundreds of thousands (!!!) of polygons in the same 16ms and also process input, recalculate the world and dynamically load/unload resources. How come?
Text is very complicated. Does your 42-year-old Emacs support Unicode? And not just accents, but whole different scripts?
See https://news.ycombinator.com/item?id=21105625 for some discussion and a good link about the complexities of rendering text.