Well they were the ones who picked GTK+. This is just inexperience kicking in here and I've never seen OpenSource developers saying such things.
It's like saying 'I've just built a house on the moon. I designed it for earth but it just doesn't fit well on the moon and it's surroundings'.
It seems even people with such resources and money like Google they can't knuckle down and just do it without whining. Just look at their browser, it looks like something straight out of XP, other web browsers for linux DEs actually fit into the rest of the desktop environment.