I support the dA presence of memes that have an element the artist must draw themselves. See the "Grab My X" meme. The ones that are image macros don't belong here. And I say this as someone who likes and makes macros.
I don't follow and memes on DA, I'm here to look at art, and they typically aren't art in my eyes. Of course there may be exceptions for this to. I do agree with others, meme's should be put in scraps, and not be able to make front page. The site is called DeviantART after all. But alas it's the internet and people can and do what they want....
The whole issue with using (a lot of the time) copyrighted work, as mention before too does go again the "rules" here at DA and therefore should be not allowed on that basis alone, but Hey it hasn't stopped people before, why should it start now.
I'm not sure if it's because the people who submit art are no longer here. Or the people who like art have disappeared. Or dA's algorithms have changed (which they definitely have) so that meme works are actually able to make their way to the front page thereby drawing in a more meme-loving demographic causing a feedback loop. But you're right in that it's becoming less and less of a reputable art site. But perhaps that's what it takes to be profitable in this day and age.
No, but I'm serious, they are funny, at least sometimes, and maybe they are creative in a way, which makes them art. But they just don't belong to a partly serious art website. There already are seperated sites for memes, like memebase, 9gag and stuff and you can find them on 4chan as the original source of memes and internet jokes, all over. It's just not right to put them here. Same thing with demotivators, it's funny, but taking a picture and give it a tag/slogan/"headline"/whatever doesn't make them art in the way it should be shown on dA. I have to admit, it's kind of difficult, because I really like reading some drawn comics on here.