You might be right! The core issue of the ICCCM though is not that it's poorly designed in and of itself, but that it is forced to worked around certain specific deficiencies in the X11 protocol (and by "specific" I mean "easily fixed in the next protocol bump", as opposed to "warrant an entire redesign"). The ICCCM authors even suggest improvements to X11 to make for a more coherent system, but sadly it seems most of them have not yet (25 yrs on…) been implemented.

My overall thesis is that the overall design of X (client/server model, mechanism not policy, extensibility) is a sound one, and that the issues cited by Wayland proponents would be better addressed by an evolution of X than a whole-sale replacement.