Boogie's video seems to cover the main concerns really well, even ignoring the part about a possible "golden era" for game-modding.
Imagine a parallel universe for a minute, where Paid Steam Workshop already exists, and Skyrim was released only a couple of months ago in its fully patched vanilla state (as it is now). The UI for a dedicated PC gamer is still a complete fucking abomination (just like in the real universe) and interested gamer >>> "me" says to himself... "fuck this shit, what a joke, I ain't buying it until they show some respect to the PC fan-base and fix the damn UI". (sound familiar?)
Clever modder comes along and creates SKYUI, and is the hero of the gaming world. He releases it to the Steam Workshop exclusively, since he wants to be paid for his brilliant work; the work that Bethesda was too fucking lazy to do themselves. I love the look of his mod so much, I would be happy to pay him $2 or maaaaybe even $4, because I can't even entertain the thought of playing the game without it.
However, for this brilliant creator to get paid (inmymind) fairly for his mod, he has to charge somewhere between $8 and $16 for it. It's a UI mod, not an official DLC, and there areno guaranteeswith it.
NO FUCKING WAY. Even more so because Bethesda will also be getting paid for someone else to fix their fucking interface.
Now, back in the real universe, is there a PC gamer alive that doesn't find something like SKYUI mandatory? 9 million Nexus downloads says... unlikely. Fast forward to Fallout 4, another dog-shit PC interface/port, and I wait for all their new game(s) to hit the bargain bins...