Picture an image with an explanation of said image written on it. That's the anti-meme.

It becomes an anti-meme, by "misunderstanding" the fundamental nature of memes. Like explaining what is happening on the image, instead of reframing it with new text.

Now picture any random image, with any random text. That's the placebo.

A placebo-meme is something that doesn't have any intent of being funny, in fact it has no way of becoming funny (other then trough irony). So yes, those 2017 memes are not placebos, because an inside-joke was already in place, making them "funny" for the intended audiance.

With the current state of memes it became hard to actually construct a placebo, since anything not even remotely funny, something containing absolutely no trace of humor could still be picked up as a "senseless joke".

Thank you for coming to my TED talk.