I disagree with a few things. The first being your first point. While it is true that not EVERY game needs multiplayer, you forgot to factor in a lot of things about the situation. The first is that Skyrim is a sequel to a wildly popular franchise. It's not going to be surprising when it sells well. That's be like being surprised the Mass Effect 2 sold well because it didn't have multiplayer (and I'm not going to comment on MP being in 3). While it may make the point that franchises don't need MP, not having it can hurt games that either don't have a massive fanbase already or a new IP.
There's also the fact that Skyrim is nearly infinitely replayable. Of course that's not a bad thing by any means, but that's not something that every game can realistically do. Skyrim is from a series and a dev team known for having giant open worlds with various quests and things to do. That means that it has an edge over games with a tighter focus that wouldn't work as open world.
My example of this is Alan Wake. I loved Alan Wake. But after I beat it, I sold it. Why? Because there was nothing to do after that point. I loved playing through the single player mode, experiencing the story and the moments it had. But once you've done it, there's no incentive to do it again. You know the story and plot. You know how things happen. There are things to get, but most of them are pointless overall. And you know what? I can't think of how they could add replayability. They could have added MP of course. But it would have likely been awful and out of place. And because of that lack of replay value and being quite different from many games (not an FPS, not an RPG, story-based, and fairly slow in terms of build-up), it didn't sell well and became cheap fairly quickly.
That arguement also goes into the 'online pass' arguement a bit. While I do think online passes are stupid overall, I think many games do get it right. And I'm going to go back to Alan Wake again to show as an example. If you bought the game new, you got the first DLC free. It wasn't just some half-assed add-on already on the disk, and at the same time you didn't need it in any way to fully enjoy the game. So not all 'buy new' incentives are bad.
Overall, you did have many good points (though the live action parts of the video where you acted like an ass made the video annoying as usual for me). But most of what you said are things that almost everyone, especially here, find obvious and will agree with completely because they all say it over and over again anyways.