In my opinion, good table governance can always substitute for the situations you would actually want safety tool, but a safety tool--being a dedicated implement--can't do certain things which table governance can. The tradeoff is that it means moving past the idea that the GM is God of the Game because you have to run a formal mechanical process. I'm sure that's going to piss some grognards off.
Does not follow. Look, being "God of the Game" means exactly that. Within the game setting/world/rules however you want to define it, the GM has last say, and often first and middle say as well. It's a necessary part of a traditionally run game (i.e. absent certain meta game mechanics put in place to deliberately farm some of that responsibility out to the players in a formal way) but even then,
someone has to do it.
This is completely orthogonal to whether or not said person, GM or otherwise, is acting like a reasonable person or a dick. Part of not being a dick is being aware of the other people at the table as fellow human beings with feelings and interests. The only reason to ever continue playing with a dick (GM or otherwise) is that the dick behavior is compensated by something else the group values (great roleplaying, long-time friend in other pursuits, whatever) enough to put up with it. Or rarely, everyone else sees that person is really trying hard to improve but just not there yet, and thus they see the game as a way to help practice out of bad habits. (It is rare, and usually people try this with way too much optimism about human nature. However, I have seen it work more than once.)
Mixing the two categories, in the game and out of the game, seldom works well for changing behavior. And when they do, it is only around the edges. Leaving aside all the specific things wrong with the X-Card that make it either useless or actively harmful, it doesn't even perform as advertised, because it can't bridge that divide. It's the player equivalent of the GM engineering a TPK because the players brought pizza to the game but didn't get exactly what he wanted.
An X-Card variant, where touching it stopped the game momentarily while everyone talked out what was going on that was bothering them--completely outside the game, could conceivably work in certain select situations. For me, that would be an automatic game killer--as in, I'm stopping the game right there--because I'm not going that close to the edge, and my sessions aren't for therapy. I think attempting to use an RPG for therapy is GM malpractice, and more likely to harm than hurt (having some practical experience with people involved in each).
"Table Governance" for normal people, in normal situations, is the same as it is at every other non-gaming social activity. Excluding the dicks, if something comes up, you talk about it, no mechanical widget necessary.