This is, stated in the rules or otherwise, a GM's job. But I think there's a turning point, when managing the rules FOR the players becomes counter-productive.
Definitely. I find that I don't care about players knowing the rules as long as they are playing ball: immersing themselves in the fiction, ready with an action declaration on their turn (even if it's sub-optimal), paying attention, making an effort to get the basics down, etc. If I have a newbie who won't even go that far, then it isn't going to work (might be the wrong hobby, wrong game system, wrong people chemistry, etc.).
There are also the players (like me) who will want to know and use the rules without GM assistance, because there's the possibility that the GM says he knows the rules, but doesn't.
I'm curious about this, but it seems like it can lead pretty far off topic. I might turn it into a new thread when I have more time to think.
Still, that's another way to get to GURPS: hold the players' hands until they can make it on their own.
It's hard to read tone on the internet, but I wouldn't use the phrase "hold the player's hands" because it often has disdainful connotations of coddling and spoon feeding. I guess you could say that's what I'm doing at my table, but it has never felt that way to me (and no player has ever complained about that). We have exciting, fast-paced adventures. Depending on the genre and system switches, games can be deadly or safe, combats complex or simple. I simply don't expect new players to read the rulebooks from cover to cover and internalize the details. That's great for hardcore gamers. I like to reach out to people who don't identify as gamers, which is a rich pool of potential players. Many of them get hooked and start buying the books and learning the system, but I don't see that as a requirement as long as they're having fun and contributing to everyone else's good time. I have a number of long-term players who are simply uninterested in the mechanical details. They just want to be part of exciting, unpredictable adventure stories.
Yes, it's a style choice. Maybe one game clamps down on damaging moves while another allows easy whirlwind attacks. But I wouldn't say GURPS is just as simple as the next game.
I would say that GURPS is more complex than many games from the GM's perspective. It takes some time, effort, and skill to make all the decisions about what elements of the system menu you want to include. Once that's done, though, the complexity is up to each group. I teach kids to play GURPS (or variants) regularly. Middle-schoolers have no trouble at all, but even elementary kids do just fine. My ten-year-old teaches his friends and cousins how to play and they build characters and have adventures without my help. Do they get everything right? Not at all, but they've got the basics down and have a blast. That's the whole idea, right?
In any event, I didn't mean to focus so much on GURPS. My intent was to follow from the OP and use it as an example of a purportedly complex system and how I've succeeded at introducing it to non-gamers. Your original question, of course, seemed more about convincing existing gamers to try different systems. In my experience, that can be more difficult, partly because people like what they know, but also because they have invested real effort into developing expertise in one or more systems and may not enjoy the process of starting over with a new system. (I'm sure that there are many other reasons too.)
I don't mind that as a player. I'll play just about anything that someone offers to run. But as a GM, I'm comfortable with GURPS or 5e (or any earlier version, really), and willing to do Call of Cthulhu, Traveller, maybe a few other boutique titles. Beyond that, my time is finite, and I don't really want to spend the money and time to learn new systems well enough to run them. (With GURPS being such a toolbox, I'm always more inclined to just customize it for different genres.)
