I originally shared this opinion (that GW should be usable on all corpses) as well and made my own post about it, but I’ve reconsidered since then and I’m fine with how it is right now.
I still wouldn’t mind using it on all corpses but it does add a layer of strategy to not be able to use the same tactic at all times and it can be played around. Try luring a fleshy enemy from elsewhere to use their corpse or use Lawbringer for Sanctuary and Decrepify, there’s lots of potential solutions.