The term you're looking for is linguistic prescriptivism. This is when people believe that one form of English is "correct" and therefore any deviation from what they believe to be 'proper English' is incorrect and thus exemplifies the lower intellect of those using the slang. Thankfully, linguistic prescriptivists are laughed at most of the time in my field, because anyone who truly thinks that there is one form of English which holds more value than any other form is a moron.If the point you're arguing is that we should purge the English Language of words and collocations such as "so much win", "so many feels", "I'm down for that" etc then I appreciate where you're coming from but quite frankly you're wrong. Why is it that these words and phrases hold less value than other words in our mental lexicon? And, how is it that a person's intelligence is tied up in the language they use? There was a myth perpetuated by Jean Goss who said that teenagers only know 800 words, which "isn't enough to get them a job"; it's this kind of person your statement sounds like. And, fun fact, she was proven wrong many, many times, because there is actually no way to be able to tell the size of a person's vocabulary truthfully, we can only estimate. If these words and phrases like "epic" are part of their vocabulary, what harm are they doing there? People aren't going to sound like Jane Austen when they type because excessive verbiage on the internet is pointless, and quite honestly makes you sound like a tool. If your 26,000 word vocabulary insists that you type every post in prose then so be it, but for other people, conveying the same idea in simpler terms is a lot more convenient over the internet because, well, who are they trying to impress? It seems like you might have some kind of obsessive need for validation, which is manifesting itself in your own outrage at 'youth culture'.
Some more fun facts about linguistic prescriptivism for ya. Many people believe that it's a cardinal sin to use the word 'their' as in its singular form, as in: if a man or a woman wants to debate language with me, I would always love to hear their views. That sentence, whilst sounding pretty innocuous to the rest of us, should make any prescriptivist gasp in horror and tremble with fear, because the use of the exclusive 'or' suggests that the antedecent to 'their' is singular - a man or a woman. Other things prescriptivists have tried to combat would be the use of 'hopeful' as an adverb. Now, hopefully, you would disagree with that radical step, right..?
Ice cream was considered the improper form of 'iced cream'; in 1586 the word 'exasperate' was criticised for being "preposterous and confusing"; Jonathan Swift objected to 'banter' and 'communications' in 1710; Thomas Jefferson was attacked for using the English word 'belittle'; in the 1800s an Englishman waged war against the Americans using 'great' instead of the English term "splendid"...
Can you see what all those have in common? That's right, they seem ridiculous and antiquated. But I hope this shows you, dearest OP, that people have been fighting the battle against the common parlance for centuries, and all that they've achieved is some kid on a message board using their stupid opinions to disprove someone's uninformed claims. People will continue to talk how they want to, and how their language evolves to allow them to speak, and people like you will continue to moan and whine about it. And honestly? No one will care.