Of course the article is actually about writing a digital DM not a player. But isn't the main problem with this defining win conditions? Pretty easy to define win condition for chess or go. Now, I haven't really played DnD (much to my sadness), but how do you win? edit: I know the answer but I'm making a point with my question
>but how do you win?
When you've provided a fun and engaging experience for your players?
I do mean this seriously. Being a DM is about making sure the players are having fun and always giving players something interesting to do. It shouldn't be too easy or too hard. The things should have some variety, you have to be able to adapt to what your players decide to do. Just because you have some cool stuff planned doesn't mean they'll find it, you can guide them a bit, but don't funnel them and accept they may not see your cool stuff, you can always save it for another time.
I guess my point is, keeping player fun and engagement high while allowing the game to run its natural course would be what I would think of as the win condition for a dm. Finding a way to measure this and provide this seems like a fairly difficult task though.