I heard the book has a cheesy ending while the original SCP version leaves it open.

My opinion is that SCP-3125 is something like game theory, or death anxiety, or knowing the most effective way to make money (which is applied game theory), that if everyone thinks about it too much, destroys the world.

These are your type 4 antimemes. Death anxiety leads to the rational conclusion that nothing is worth doing so you might as well just die immediately, and this takes the idea with it. (Healthy humans have developed irrational ways to suppress this.) (Particularly unhealthy humans might also realize that society and the human race don't matter, or that other humans existing are suffering for no benefit.) Perfect knowledge of game theory leads to a cut-throat world where not much survives, again taking most of the idea with it, as well as every idea that's not part of the optimal winning strategy.

Time matters in some of the categories there. What if a meme (I don't know, money, the tragedy of the commons, some future cult of the dead or whatever) works as a great filter and wipes mankind and any civilization that develops it at some stage? it is an antimeme even if, for some thousand years, it became locally popular? Something that erases itself or whatever spreads it over a not short period of time qualifies as antimeme or not?