People don't have to explain their preferences in a rational way, they will just switch away from GTK3. It's cheaper.
Successful developers will try to interpret these users' feedback in a self-critical, introspective and positive way, and tweak their product based on the feedback. As opposed to continually challenging the giver of the feedback to explain their opinion in more detail, as if by repeatedly digging deeper and deeper into an opinion, you will at some point find some fundamental logical contradiction in their views that will make them re-evaluate their life philosophy on why they just don't like GTK3.
I for one think the two opinions given above are perfectly clear ("GTK3 is becoming very GNOME3 specific", "As a user, I don't want them") and can't see why further clarification is being requested. If you really need clarification on these perfectly clear opinions, it is your problem.