This is not entirely true. A few GNOME developers within GTK/Mutter/GNOME Shell are paid to work on this kind of work at least part-time. SourceHut also pays Simon Ser to do some Wayland work, whether that is maintaining wayland-protocols or something else.
> With the introduction of wayland they seem to be more set on forcing developers to choose, like they really are blocking tray icons now.
This is also not true. GNOME has designs for tray icons in their GitLab repo. The thing that is blocking better tray icons in Linux is a lack of interest in finishing the protocol proposal. The ticket hasn't seen much traction in the last couple of months.
https://gitlab.freedesktop.org/xdg/xdg-specs/-/merge_request...