Imagine a table at a wedding:
There’s a conversation going on. Everyone can hear it but not everybody has to talk. There’s rarely an embarrassing silence, though, because there’s at least one person there who just really wants to get to the heart of the matter of whatever this conversation is about and so will start talking if there’s a lull.
Once in a while, no matter who you are, you will be called upon to perform simple, well-defined tasks. “Can you pass the peas?””Are you going to hit the rust monster or do something else?” This is easy for pretty much anybody and doesn’t put you on the spot.
Nothing necessarily stops you from doing something mechanically novel like, say, putting olives on your pancakes, but the conversation and the meal will keep on even if you don’t.
Nothing stops you from interjecting with your own ideas “Well I think Sigmund Freud was full of shit!””I think we should tie the displacer beast up before we try to sell it to the mountain gnome,” and thus taking the conversation in a whole new direction, but the conversation will keep going if you don’t.
This is normal, this is what all kinds of people do every day. They are shy and insecure or apathetic about the subject or the company they’re in and when they become comfortable or the conversation moves to a place they have ideas about, then they talk.
In D&D, as a player, you can (often, not always) choose to grapple hard with the scenario (“I look in the desk,””I write ‘xvarts suck’ on the wall with a rock”, “I mix the growth and shrinking potions together to see what happens”) or you can sit back and roll dice when it’s necessary and just regard what the DM and the more aggressive players are doing as entertainment, like a movie where you have a choice.
In other words, D&D supports several playing styles simultaneously (assuming the DM’s any good). In a good game, everybody’s playing the game they want to play, even if it’s eight different games.
Right here, I should say something: the ‘passive player’ is rarely forever passive.