That is not what they are doing. They are aligning with the consensus of science. No serious primatologist thinks there’s any chance Big Foot is real, for example. There’s no plausibility to the hypothesis, no quality evidence pointing in that direction, and there’s been no shortage of people looking. Big Foot does not exist. Science can be very confident saying that. Nothing is ever 100% in science, but at some point you have to call it. It has become an extraordinary claim, and thus requires extraordinary evidence to change the scientific consensus.
If I tell you there’s a teapot orbiting Mars, but there’s zero evidence for that, and NASA has said there isn’t because they’d have seen it with their probes, that’s pseudoscience. I’m making a claim with no evidence, and an extraordinary one at that. I can swear that evidence will appear someday of said teapot if you’d all just hear me out, but that isn’t science.
Wikipedia’s job is to try and ensure quality information. That’s what they are doing. Claiming Big Foot might be real is no different than a Trumper claiming he won the election. The quality of evidence is the same.
