The issue you're pointing to seems to be more a function of limited resources (see O.P's comment about there only being one real maintainer for GTK+) than deliberate neglect.
Over the years, I've gotten various patches into various GNOME components. In rare cases, just posting in bugzilla gets a response. More often than not, it has involved prodding people on irc and mailing lists and spending some time advocating for my technical solutions (or just sending a reminder that it needs to be looked at). Sometimes I have spent more time doing this than writing my actual patch.
I can't say I haven't been somewhat frustrated by these experiences, but I don't think it's right to ascribe sinister motivations to the core GTK+/GNOME developers. As far as I can tell, they're just really busy people.