The problem with the shader nodes is that one cannot expect, emphatically, the image texture to be directly attached to the root node.  There can be intervening procedural nodes that dramatically change/enhance it.  These would not be transmitted to other applications.

This isn't really a difference between MAT poses and the newer Materials/Material Collections as it is, between what can be done to replicate them in other applications.  Truly, even the archaic material system cannot be faithfully reproduced in other applications - but it involves less dependence upon procedural models than the shader node system.  The shader node system employs a more complex system.  The solution is better export/support from Poser - which doesn't exist!  Poser doesn't do any baking of the shader nodes so that the effects are transmitted.  Not even the official hosting.  The only solution, at this stage, would be a third-party 'baker' to crudely transmit the shader nodes to the targetted application.

That's all that I'm saying. :)

ETA: apparently the post to which I was responding went bye-bye.. :(

C makes it easy to shoot yourself in the foot. C++ makes it harder, but when you do, you blow your whole leg off.

 -- Bjarne Stroustrup

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