I'm getting tired of seeing "X11 is being replaced because it's old", no one who actually understands this space thinks that. It's designed the way it is because it is old, this is completely true.

But the way it is designed is the reason it is being replaced, not the age of the project. If we got it right back in the 80's then no one would even be talking about a Wayland today. Today there are new use cases which require massive protocol breaking changes that wouldn't just work in X11 as is