It's less that people should be able to copyright a meme, though it is a creative work that might warrant it, but more like a whole lot of memes use pictures and clips from copyrighted works and the likenesses of people, and as the law is written people are not legally allowed to do that, however much it is entirely glossed over.

Dropping copyright every 20 years seems reasonable with the speed of internet culture and technology, and funny enough that's very similar to the length that copyright started as: 14 years plus an optional extension of another 14 years. It might be controversial, but that seems absolutely more reasonable than the 120 years that corporations get today. Can you imagine if people actually waited 120 years to play old Nintendo games? Chances all but a few collector pieces among the cartridges would have become rust already. It's not a reasonable length for technology-based media.