Gentoo user here, just to side-step any Ubuntu fanboy responses.
Why are two competing display server stacks considered a problem in this case?
Over the years we've had countless situations like this
The various desktop environments, package management systems, initialisation systems, boot loaders, audio stacks, etc. etc.
Often seen as the benefit of open-source software.
The ability for multiple software components to exist that fulfil the same function. May the best man win.
Innovation and progress comes from each project trying to out-do it's rivals.
Often these competing solutions have a single distro or company behind them, driving development forward.
Why is Ubuntu's new display server, competing against X.org and Wayland any different?