Can you write an application which uses screen capture on Wayland, and which works equally well regardless of compositor?
If not, then Wayland doesn't support screen capture. Individual compositors might, but asking developers to implement five separate screen capture protocols is a big ask.
You can. The standard is new, but it exists, and now works on Gnome, KDE and wlroots based compositors https://wiki.archlinux.org/index.php/PipeWire (read past the intro paragraph to where it talks about the various backends available)