Yes, and so is every other human language. Language is always changing, evolving, and adapting to the needs of its users. As long as the needs of language users continue to change, so will the language. But reading Shakespeare's writings from the sixteenth century can be difficult. If you go back a couple more centuries, Chaucer's Canterbury Tales are very tough sledding, and if you went back another 500 years to try to read Beowulf , it would be like reading a different language.
Language changes for several reasons.
First, it changes because the needs of its speakers change. New technologies, new products, and new experiences require new words to refer to them clearly and efficiently. Another reason for change is that no two people have had exactly the same language experience. We all know a slightly different set of words and constructions, depending on our age, job, education level, region of the country, and so on. We pick up new words and phrases from all the different people we talk with, and these combine to make something new and unlike any other person's particular way of speaking.