Wayland seems ready to me but the main problem that many programs are not configured / compiled to support it. Why is that? I know it's not easy as "Wayland support? Yes" (but in many cases adding a flag is enough but maybe it's not a perfect support). What am I missing? Even Blender says if it fails to use Wayland it will use X11.
When Wayland is detected, it is the preferred system, otherwise X11 will be used
Also XWayland has many limitations as X11 does.
because for most of them, there is nothing to port them to. Wayland is incomplete... by design.
What are advantages of being
I know Wayland is simpler but it should cover almost every highly requested feature if developers need it.
"almost" being the key word there.
You have a gross misunderstanding of what a display fucking system should do. X11 nowadays provides the same thing to apps as Wayland, except some bad design hacks that have become fundamental to writing Linux apps that are essentially workarounds for X11 sucking badly.
NOBODY uses X11's font system or widget system or vector system nowadays. X11 provides you with a render plane and some other bullshit and the toolkit does the rest.
Which is the same as Wayland. Except Wayland actually has a properly designed and standardized way of doing things through the extension system, as in X11 everything is cobbled together from hacks.
A good example is absolute window positioning. Wayland doesn't have it because it's been found that it wasn't actually really needed, people did things that way because something that's essentially a clever hack had become the de facto standard on X11. Same thing with how X11 apps do window captures.
Generally, Wayland is a great leap in Linux desktop system. We're catching up to what MacOS and Windows did 20 fucking years ago.