I think in some cases yes it is. But I've just given all sorts of different examples of gatekeeping, and I don't think that in all cases you can say it's about feeling superior over other people.
Take the example of the person who really wants to be into Magic:The Gathering, but can't afford it, so he just cuts out some 3x5 note cards and labels them, "Island", "Mox Pearl", "Ancestral Recall", and what not and then goes to the local fantasy gaming store looking for acceptance, validation, and affirmation. Suppose, as is likely, he doesn't get it. It is likely that some of the players present take a certain pride in their collection and feel a certain since of superiority over other people on account of their possessions. Greed is a thing. But feelings of greed aside, the player may have a deck that isn't legal, or isn't legal for the format being played. It may be that it's a sanctioned event which requires real cards. The player may not yet be very conversant in the rules and be annoying to play against. He certainly isn't conversant in the culture of the game and clearly isn't aware just how much of a cultural faux pas he's committing. Most of all, he's just annoying to play against because the art on a card is a functional part of the card. It allows someone to see the game space and understand it from across the table in a way hand written cards don't. Even someone with the best of intentions is going to be acting out of pity and not enjoying the game the way he normally does.
So this player fails to get his acceptance,validation, and affirmation. He is at the least likely to be subject to some gentle joshing, which likely won't feel so gentle to him. He's not going to be "part of the group". He's going to be still an outsider.
This is a complicated story that could go down in many ways. The player being a white male is not going to make him more likely to be accepted. There is no "white privilege" card that lets you use index cards in an MtG social setting with strangers. In settings I played in across multiple cities, in some cases you could use a fake, but it had to be a good fake and you had to be able to demonstrate that you owned the card and the only reason you weren't using the real one was to avoid play wear. Is it fair to have acceptance in the group be based on how much money you can spend on a trivial game? Maybe not. But that's a whole different sort of gatekeeping than the simplistic definitions being offered here, and it's one I've seen far more often than the simplistic notions of sexism or racism that are being offered up here.
While we are on that, I don't in the slightest deny that there have been many examples of people who were made to not feel welcome on account of race or gender. But history is a lot like a stained glass window that is shattered. It has many pieces. You cannot pick up a single piece of it, hold it up as an example, and say that this is what the whole window looked like. One of the evils of racism or sexism is that when you encounter scorn, the presence of racism or sexism tends to lead you to conclude that the basis of that scorn is always race or gender. And often you may be right. But one advantage of being a nerd is that you learn that there are plenty of instances of scorn that have nothing at all to with that.