What do you mean? The axe struck Thanos' chest and that wasn't enough to kill him instantly, even with the axe embedded in his chest and Thor putting more force into it wasn't enough, that's why Thor tries to cut more vulnerable parts such as the neck.
The axe can cut limbs, the neck, and cause large gashes on Shigaraki's body, but that is not enough to finish him off, and if Thanos can physically stop the Stormbreaker by
blocking its handle, then Shigaraki should be able to do the same, but as I said before I doubt he can even get close enough to Shiggy.
