Although Shakespeare's English may sound complicated to the modern reader, it really is just an early form of the English language currently in use today. There are a few differences, of course, between today's English and Shakespeare's Early Modern English.
One major difference is that many of Shakespeare's plays and other works were written in a rhythmic poetic form called iambic pentameter. This poetic measure requires the author to generally use a rhythmic cadence of 10 "beats," or syllables, per line. Contributing much to the beauty of Shakespeare's works, this form also adds some complexity for the modern reader not familiar with this poetic style.
Whether old or newer in its form, English is always changing according to cultural and artistic needs and trends. For instance, whenever Shakespeare needed a new and exciting way to convey his ideas or advance a good story line, he just made up brand new words to fit his creative vision. In fact, he used over 20,000 new English words in his combined works, and of these, it's estimated that he invented about 1,678.