Just gonna point this out right now. No Kaneki cannot handle deconstruction. His resistance to biological deconstruction and overhauls "
Earth Manipulation,
Healing,
Resurrection,
Biological Manipulation,
Fusionism,
Deconstruction, and
Matter Manipulation" are completely different. Tomura Shigaraki can resist deconstruction and has a way stronger deconstruction Overhaul's deconstruction, yet can still get one shotted by the Overhaul quirk. Keep in mind the Decay quirk is a copy of Overhaul's quirk but stripped from all its reconstruction/other exclusive abilities and had its deconstruction effects amplified on steroids.
And no saying Shigaraki is immune to his quirk isnt correct, the overhaul quirk works on Kai himself. Shigaraki is also accepted as being resistant to deconstruction.
So keep that in mind that the person who has more arguments than Kaneki for resisting Decon and is literally using the modified version of the overhaul quirk cannot resist being one shotted by it