Let me make one thing clear here: This is a discussion on the concept of paid mods, not how Valve implemented it. I personally believe modders should be entitlted to some form of payment for their work, and this isn't just for modding itself- It honestly boils down to a simple fact: Talented people should be compensated for their work.
It wasn't "scrapped", It was taken down until they can find a better way to implement this system. Likewise, Skyrim wasn't exactly the best choice to do this, as their community has had free mods for years now, thus why it caused the entire Nexus community to rush out in an uproar. The hilarity in this is that Valve actually warned Robin Scott, owner of Nexus Mods, to be prepared for the fallout. It's almost as if they knew this backlash was imminent.
Modders didn't even get 25% anyway, Valve got 75%. Bethesda got nearly 10 - 15%, and the creators themselves get nearly 10%. Hell, even 5% of Valve's cut goes to the Nexus Mods websites, which was and is the main server provider for Skyrim mods in the first place. However, i do agree with your argument that there should at least be a donate button. Nexus Mods does it right, Steam blew it up like a microwaved egg.
And for gods sakes, there was so many troll mods and protest mods on the workshop during this that it was sickening. 100$ for a golden potato?