Humanoid animation looks different on multiple humanoid rigs

Hi im really having trouble understanding whats going on with thee animations.

I have a couple of assets from the store, crafting, rpg combat, villager animations etc, they all work really well on the rig they are designed for.

But if I try them out on other humanoid models the hands never align, they are always off.



This is meant to be an idle animation for holding a 2h item but as you can see the hands on all models are just completely off.

I haven't made any changes to the rigs, they are all mapped and in a T pose, rigs and animations are humanoid.

Pretty much all animations where both hands are required e.g. holding, throwing. actions the hands are just way off. I thought that the whole humanoid/mecanim thing was meant to make it easy to reuse animations across different rigs but at this point I might as well bite the bullet and learn blender.

Any help would be greatly appreciated,
Thanks.

 

another example