I do not get this session 0, consent form or red card mindset. I have never been in a group where this would be needed or required and I have been GMing since '93.
I'll admit to being slightly unsure sometimes about the Red-card/ X-card system. But then again, I also heard a horror story from a friend of mine. When he was younger, and running a game for his current wife, he had her female character almost sexually assaulted. He got caught up in the RP and the scene, and didn't think it through. He feels horrible about it, and she forgave him years ago, but it sticks with him as a reminder.
For myself, I don't think I really need a card, because I like to think the players know they can speak up, but I certainly can understand the reason it exists.
As a GM, I do set boundaries. The players cannot be evil. The players cannot make characters with backgrounds that would prevent them from working in a group. I call it the "do not be a jerk" rule.
If I recruit new players or form a new group of strangers, then I meet people separately to see if we will get along and if they would want to play in my style of game. I spend a lot of time developing campaign worlds and scenarios for players. I will usually sit down with players to discuss whether a race/ancestry/heritage/species/etc, class, etc will fit. I always provide a list of available or excluded options. I do often exclude classes or race/ancestry/heritage/species/etc for certain worlds or campaigns. I will also work with players to build a custom class option.
You realize that sitting down with your players to discuss whether game elements will fit, and talking to them about your world, is a session zero right? Like, the thing you say you don't get and don't require is the thing you do.
If a player shows up with a mindset that they can dictate, then they can find another game and that it cool. As a GM, I want to have fun too and that often shows up in my homebrews because I want to have different themes for my campaigns.
Well, that depends on what they are dictating for me.
A player comes in and says "I have 1 MILLION gold and an army of servants equipped with magical swords that fire swords!" Yeah, no, bad joke. Let's be serious.
But, I myself have set terms before. I played a campaign I was very excited for, and to tie my character to the setting I made someone who had a life in the city we were based out of. Specifically, he had a wife. However, I told the DM I had zero interest in any story where my character's wife, who loved him dearly, cheated on him. I knew we would be away for long periods of time, I knew the DM would put her in danger, but I told them I did not want a story where she was unfaithful to my paladin. That... is dictating. That is me telling you the DM what is acceptable, but also... I don't think that really crosses a line most people would find objectionable.
This is why I really don't like hard stances on this issue. Obviously there are players who are terrible and say or demand stupid stuff, because they have the maturity of a 5 year old. But also, there are players who are mature, respectful, and just are looking to establish boundaries. And I never really trust a DM who refuses to let me set boundaries, because they must be the sole arbiter of everything. It begins to feel like they don't care about my enjoyment of the game if it might infringe upon their "vision".
