For one thing, Wayland is a protocol, not a specific piece of software. But mostly, that progress has been non-linear. A ton of it is not about writing code, or even about Wayland itself; much of it tied into the modernization of the Linux and general open source graphics ecosystem, moving it away from being oriented around X.org specifically and implementing modern features like generic buffer management and kernel modesetting. A lot of setbacks have been simply waiting on NVIDIA to support these modern facilities well in their still-very-popular proprietary drivers.

HDR support has been in the works for years. Why? Well, nothing terribly specific to do with Wayland: there has been a ridiculously deep dive into the entire space of color management, wide-gamut colorspaces, etc. to try to build HDR protocols that don't merely just get things out the door, but ideally support current and future use cases for the foreseeable future, have good backwards compatibility and handling of unaware apps, etc. These things are non-trivial and can't be solved by writing code or staring at GDB. (Not to mention there are few drivers that can currently support this, so it's also a bit of a chicken and egg problem.)

That is to say, Wayland is a lot less of a software problem than it is a design and social problem. And as you can probably see, ultimately, Wayland will be nobody's favorite, but hopefully with time, it can at least be everybody's favorite.

Ever heard of GNU Hurd ?

PulseAudio is still not there after 19 years.

On the other hand, PipeWire is?

Thank $deity, it is. PipeWire actually works well.

It has already surpassed it.