Window positioning? You cannot position the window, you cannot send a hint, nothing? So my pop-up with GTK4 will randomly be placed somewhere, anywhere, without any control. OK, GTK4 went further and also removed popups without the parent, so you hack that with an invisible anchor window and then write platform-specific code for sane platforms that CAN, of course, move the window. And let's not talk about window icons that you have to put somewhere on the file system?
Have you considered if someone wants to make a compositor where each window is projected onto a facet of a hyper cube and must place windows in 4 dimensions? These are important use cases we should support, we should make cross platform software as difficult possible to develop for Linux by removing features that have been standard on desktop operating systems for decades.
I must correct you! Wayland has not and indeed cannot remove features because Wayland is a “protocol”. It is the compositors that are removing features.
This dilution of responsibility should make you feel much better.
It's not technically behind on window positioning. Rather, it was a deliberate choice not to support it. You can very reasonably object to that, but it is sorta a necessary measure to prevent clickjacking.
And common sense mitigations: if a new program I've never seen before drops an actionable control under my cursor, maybe just default to not immediately accepting the next input to it so I have a chance to see it.
I mean, you can create alternate APIs that would work for the pop-up use case: you could have a command to create a new window positioned relative to the current window’s coordinate space.
That limited capability still has a risk of denial attacks (just throwing up pop-ups that extend beyond the current window’s boundaries), but those can be mitigated in a number of ways (limit the new window’s boundaries to the current window’s, or just limit how many windows can be opened, etc.).
What's missing?