I am aware of the origin of the word. I am distinguishing between the generic notion of a meme (which as you pointed out simply means "transmittable idea", which is an incredibly general concept) and the specific notion of an Internet Meme (and, as in OP, 'meme culture', which surely refers to Internet meme culture, and not the culture of transmittable ideas in general).

The later misuse of the word meme to refer only to image macros is also a separate shift.