They still had 10 years to do that. complaining about the lack of tooling they didn't develop is idiotic, they are in charge of the language themselves.
Well, not all people have the expertise or willingness (in case of volunteers) to work on this. Switching to Rust would allow them to leverage somebody else's work.
Also, GObject itself made a lot of sense in an era when C was dominant. Maybe now, not so much.
Switching to Rust isn't going to solve Gnome management problems. You could make the case that they should ditch Gtk and adopt Qt, it would actually make more sense than rewriting Gtk in Rust given the amount of work it represents. But you complaining about the tools that don't exist is still ridiculous, the problem is why these weren't developed at first place.
Also, GObject itself made a lot of sense in an era when C was dominant. Maybe now, not so much.