X11 was designed to everything like OS, it's display server, gui library, font manager, printing server and more, X11 was ment to be like qt or gtk, you tell it that you want to display input and it will draw it for you, the issue now it that basically every app now display every window as one bitmap, because we do not want to use 98% of the x11. Also why do you think there wasn't much development activity in X for years now? There is so much wrong with it's state that nobody wants to work with it. It's like talking: why someone would like to use rust or go or c# when we have cobol? why not just write cobol extension?