Well, that's only a partially true statement. It is hard to understand, but more so because of all the thee's and Thou's going on. Also, the style of speech during that time is incredibly different. It's very flowery and over the top, mainly because people liked to be polite, but still insult each other. So they would insult each other with wit. The idea is that you wouldn't be smart enough to understand the reference (which, was just another jab to you, because then you were stupid.) Or, if you could understand it, then it was all played off as a bit of good humor, but you knew what was going down.
Some Shakespearean insults?
I do desire that we be better strangers. Puny, puke, hasty-witted lout. Because, you know, in Shakespeare's time being a quick thinker was a most terrible insult. (If you really want to get into it, go here for create your own Shakespearean insults.)
So, Iambic Pentameter. What is it, exactly? Well, Dictionary.com tells me it's "a common meter in poetry consisting of an unryhmed line with five feet or accents, each foot containing an unaccented syllable and an accented syllable."
Ok, so that was a bunch of mumbo jumbo. Basically, you get about 11 syllables, and five of them are stressed. Not just normal stressed, but every other syllable is stressed. Your voice goes up and down with each syllable, kind of like the crest and fall of a wave. Think of it like bobbing on the ocean. Something completely outdated that no one ever uses anymore, right?
Our generation (basically from age 10 - 30 or so) are masters of Iamb and we don't even know it! We naturally alternate stressing our words. Like, if I were to say my name is Cassy, it would roughly sound like "my NAME is CAssy." Unstressed, stressed, unstressed, stressed, unstressed. (It is also half a pentameter, but that's just coincidence, I feel.)
And while, I will concede that we don't talk in pentameter and rhyming couplets like Shakespeare, Iambs have become ingrained into our everyday speech, in a way that it wasn't in Shakespeare's time. He's considered a master of Iambic Pentameter, because their speech patterns were different then, so it was a bigger deal. Ok, so putting everything in five stressed syllables and RHYMING them, still kind of baller.
So, if you are ever forced to read Shakespeare ever again, just try and think of it in terms of your every day speech.