Mm, I don't know. I mean, I get your point, but I feel like this is like... saying safewords are bad and more harmful than not because bad Doms will take it as encouragement to push hard until they make their sub use their safeword, and that as long as they stop when the safeword's called any other behavior is fine, and if the sub didn't use the safeword and says afterwards that they were uncomfortable then they should've just used their safeword at the time and don't have a right to feel uncomfortable now...
Like, any type of tools can be pounced on by the abusive to abuse further. Some GMs will use lines and veils and the X card to purposefully push right up against their players' triggers, and some players will do the same, there's no doubt about this. But those are awful GMs and players, and the only real solution with those sorts of people is to not play with them or (if you're the GM yourself) kick them out of your game and let everyone know that crap won't be tolerated at your table. There's not going to be anything that helps with people like that. If they hear that something bothers you and light up and go "oh, now I can poke and prod at this thing and get their hackles all raised, lol u triggered?" they are also the sorts of people who, if safety tools aren't being used, will note discomfort in your expression or body language, or when you try to speak up without the use of safety tools, and do the same thing.
I get that safety tools are definitely not a panacea; like I said above, really what it comes down to is that some people just... need to be told they're not welcome at our tables. GMs especially need to be very clear about what they will not put up with. And you talk about it putting the onus on the marginalized person to speak out, and like, I won't lie, to some degree that is true. But there aren't real ways around that that I can see. An alternative might be for DMs to just say flat-out that certain things aren't allowed at the table, but what if I'm bothered by something that they don't include in that list, which they can't reasonably be expected to know I'd need them to leave out? Another alternative might be the DM or other players asking me if I'm uncomfortable and if the scene is okay if they feel like they notice me looking or acting uncomfortable, but that feels like a really iffy option to me; the onus is still on me to say "yes, I'm uncomfortable," and being put on the spot like that might make the feeling worse, or I might not have been uncomfortable in the first place and then there's a well-meaning but frustrating "but we can definitely leave out X if you don't like it" "no, X is fine" "are you sure?" back and forth.
I am marginalized, on several axes, and have some stuff I definitely am uncomfortable with and would rather avoid happening in games, and would be super happy to have a way to discreetly say "nope" to a scene without having to explain myself. In my experience, all versions of the safety tools stress that no one need explain themself, that no one is grilled about it, that no undue attention is even brought to it. And in my experience, all the tables I've been at that have used this system have felt a lot safer for me to play it. The GMs who use it and the players who don't get argumentative about it being used are communicating just by its use a willingness to listen and respect if I do need to bring up a problem. And they might be lying! They really might be. But people can lie about anything using anything, and I'm glad a simple method exists these days where I can look at a table and relax a little and go "ah, if I get uncomfortable with a scene, these people won't expect me to bottle it up and keep quiet lest I ruin their fun."
Sorry for the tl;dr, basically what I mean is that while you're right that yes the community itself needs fixed, I don't think it's right to say that a method of making the community as it is safer to navigate is bad because it's not outright fixing the community itself. I'm not sure there is a way to fix the community itself, and if there is, it'll be a slow process. In the meantime I feel like these tools make it feel easier and safer for me to say if something is bothering me, or to make sure things that I know will greatly bother me will never come up in the first place, and I think that's incredibly valuable if not vital. So it feels unfair to frame it as "bad and in most cases harmful" rather than "imperfect and there will always be other things necessary on top of it."
...good lord I'm sorry that reply was so long. tl;dr I find safety tools to have improved my own experiences drastically and while they're imperfect I'm bothered by them being called "bad and harmful" just because they can be abused, because abusers will use anything to abuse and not using them certainly doesn't make it harder for them, it just makes me more wary of the table.
Long replies are fine! So of course you cant and shouldn't design around assholes abusing something that is a fruitless task and in the end pointless. In my mind there are 2 types of people who use X card in particular those who are acting in good faith, who are normally more conscious around issues and people, and those who are preformative about the whole idea.
People who are preformative are the people who would abuse this tool, and in my experience there are a lot of them in the community. Im really happy to hear that you have positive experiences with using X card but the majority of people who I have talked to about this only ever have negative feelings towards the use of the card. The major problem with the X card is that people use and then go "Right no need to address underling problems or talk in depth with the group I have in front of me I can just tap a sign" and I know people on this forum are in the know on how its important to be communicative with players and the value of trust. The vast majority of people who use X card don't think past the "rule". Where I believe the harmful part, come in is where people will just look at safety tools and go "Yep we are okay now we have this piece of paper".
I would also like to see more tools created by marginalised people, a lot of what i have across have been written by Cis white non disabled men and while I'm sure they are trying their very best to be good allies it just shows very clearly to me there are gaps in the knowledge and or experience.
Im really bad a TLDRS so sorry for the read!