I'd quibble with your friend on a few points. But he has some good things to say. I'll just run through 'em.
Great post, though. Great excuse to talk about the theories involved.
1. The draft is very important, to be sure, but there are always great pickups during the season. I've picked up a couple of start-worthy guys each year. You're less likely to pickup a
huge impact guy the way you are in football, but you're way more likely to fill little holes, particularly at infield positions and closer. It also, of course, depends on the league setup. The draft matters way more in a deep league, and/or one where all the owners are both experienced and dedicated.
2. Probably too simplistic. Obviously if a person offers a trade they've already decided it's probably good for them, but I've accepted lots of trades that I didn't propose and been glad I did later. That said, his advice is probably good if you need to tell someone new to fantasy baseball something useful in just a single sentence, since it rules out the possibility of a new guy getting fleeced.
3. By this, he almost certainly means that head-to-head involves more luck than Rotisserie style. Which is true. But it also creates more drama and tension, particularly in the playoffs, whereas in a Rotisserie league the last few weeks of the season can be largely symbolic or obligatory. So it depends on what you value: more fun for more people, or making sure the best team wins every time? There's no right answer. Though I'd absolutely be willing to switch to Rotisserie next year. I've only played it once in my life, actually, and coincidentally I both first used a Springfield team name then and happened to win it. Yay. I think that was my first-ever baseball championship, actually.
4. This relates to #3. He's not wrong; it's a very luck-based game. It's one of those things where being very good at it just puts you in the playoffs (and not even always then), but after that fate has to smile on you a little. No doubt about it.
Given #3 and #4, it sounds like he's mostly about making sure the best-run team wins above all else. Which is understandable.