Jokes have been in decline for quite some time. Consider that before the 60s and 70s, most jokes were long form stories that built up to a single punchline. A priest and a rabbi in a bar, a husband rushing to the hospital to see his wife, a hitchhiker stops at a convent, etc.

Then a joke gets reduced to a question and answer format, "did you hear about the?", "how many to change a light bulb?", etc.

Then, jokes just become one-liners. One sentence was all that was needed to tell a joke. "The dalai lama stops at a hotdog stand and says 'make me one with everything'".

Along with the one-liners came the sarcastic quips. "That's what she said!". "Yeah, right". "Bazinga!". etc.

Memes are just the image form of the one-liner. Copypasta are a vestige of the older story-format type of joke, sort of.