Over 8 billion emojis are sent daily. It is incorrect to describe them as "non-essential" given that they are now so ingrained in the way different populations interact. Emojis can be used independently of words. Emojis typically depict objects, but there are many emojis that represent abstract entities (such as colors or other signifiers), or have taken on an alternative metonymic meaning. With the wide array of emojis available, there are countless combinations to express exactly what is intended in conversation.
A conversation between two people can, in theory, be done entirely with emojis. If both parties agree upon a meaning for each emoji used, and both understand them well enough, they can carry out a full conversation with only emojis. A similar concept are the Kanji symbols in written Japanese which express entire words or ideas in a single symbol. So emojis. when used to this same level, can indeed become an essential and universal part of language and communication.