@peppe To be clear about that, I don't question the fact that #X11 is full of old cruft that's mostly useless nowadays. It became more than clear to me while implementing my #xmoji tool, which uses almost exclusively #XRender requests for rendering (an *extension* to X11, not part of the core protocol), because X core drawing requests are really designed for 1990es hardware, supporting color palettes with limited entries, but no alpha channel whatsoever. Similar goes for font support in the X11 core protocol, it's useless supporting only bitmap fonts with no antialiasing etc, so I use client-side rasterizing (with freetype) and XRender only for compositing the result. There are more silly examples, like the "Compound Text" encoding monstrosity, because the core design predates Unicode, and so on....
In a nutshell, a major rework of what the X core protocol supports would be necessary.
But then, you can *still* dislike a suggested solution. I think #wayland is taking the "simplicity" much too far, so now both compositors and clients (rendering windows) have to do the same stuff over and over again. It's a pointless exercise trying to create a wayland client without huge libraries (such as e.g. cairo for client-side rendering, better yet use a full-blown toolkit like Qt or GTK that already makes use of cairo), while this is perfectly possible for X.
