There may be a mixed view on whether slang has boosted the impact of the English language (or any other language) by adding more variety into common language or made it worse.
It seems like technology and human evolution has played a part in either accepting slang or rejecting it due to the isolation that is caused by not fully understanding a groups’ vernacular. Granted we don’t use certain words from the 1920’s but even prior to that the English language has elements of French, Latin, German and many others, so its seemingly logical that “modern” language would have its own adaptations.
Words like “cool”, “chill” and “peace” where typically integrated into language in the 60’s as a refection of being yourself and expressing yourself freely came with its on linguistic accompaniments. Most of which are still used now interchangeably as a greeting, farewell or to describe a state of being.