Not unreasonable imho. GTK does have very few resources, they're not exactly like Qt with hundreds of full-time developers. So yeah, if you don't like how things go, help out.
I don't think you can blame Ottens and others for wanting to fundamentally improve GTK and bring it to the level that it can finally do proper CSS theming - it's long overdue. That creates breakage for a while but the alternative is standstill, which is not a real option imho.