I'm guessing you're probably not familiar with the Smash Bros. franchise.
These are basically universally beloved fighting games with a unique game mechanic. It's lighthearted and has very little to do with the original games the characters come from. The characters are drawn from all kinds of Nintendo games, old and new. They each have signature moves based on their moves in their own games and fight on stages based off of those games, but that's about as far as the resemblance goes.
The point of the game is to have fun pitting unlikely heroes and villains against one another. Like, say, Snake vs. the Poekmon Trainer. Getting upset over the game not respecting Snake's legacy is a bit silly, IMO, but whatever floats your boat.