The memes and comments there actually helped me a lot with learning expressions, idioms, and “shorthand” that modern German speakers use. Little everyday nuances I would have missed from just reading books.
Hmm, actually a lot of the memes there are parodies of the English ones you find on Reddit. Just saying that a lot of them are almost nonsensical to someone not familiar with Reddit's English language meme culture.
That's probably a bad idea, r/de delights in literal translations of English expressions and memes. Many comments are completely incomprehensible to outsiders. It's a parody on the English-speaking parts of reddit and not a good place to learn German. Not unless you can distinguish when they're butchering the language for fun from when it's actual colloquial German.