XOrg was predominantly used as a useless middleman between a compositor and a window manager communicating with each other. Just because the wayland compositor is “one big important process” doesn’t mean that the whole architecture is more complicated.
Multiple IPCs make the whole stuff way more complex, there is a reason why we have a big monolith as browsers and not some `curl | htmlRender | jsInterpreter` Rube Goldberg machine — the unix philosophy is not the pan ultimate design, it works in some cases and is utterly broken in others.
X11 != the lowest common denominator implementation of X11. Nor was everyone using it with big heavy compositors (honestly, the only reason I used a compositor for years was intel removing sync circuitry from their iGPUs).
And Wayland did not stop requiring multiple IPCs, in fact it mandates them as several features require passing data by secondary channels, not just for Portals et al - some don't even have any described way to reliably pass the information that I have seen (like how to pass around cookie to let one application activate window of another? Or maybe the spec is such a mess that I'm looking at completely wrong place when I tried to fix ability to reliably switch between applications without extending compositor).
And yes, the architecture is more complicated in practice, otherwise it might have reached parity with what X11 did after as many years - like input method support. Unfortunately it's so broken that you have multiple versions of it in practice, it requires extra IPC in practice, and at least in my experience just does not work.
Multiple IPCs make the whole stuff way more complex, there is a reason why we have a big monolith as browsers and not some `curl | htmlRender | jsInterpreter` Rube Goldberg machine — the unix philosophy is not the pan ultimate design, it works in some cases and is utterly broken in others.