Mandarin's writing system, with its 20,000+ characters in a modern dictionary, is too complex to achieve a widely used lingua franca status around the globe. In contrast, English is much easier.
The argument
The main difficulty is that Mandarin uses a written character system. Languages like English, Russian, and Hindi use an alphabetical system, which helps users learn the language easier as speaking, reading, and writing in these languages are related, intertwined processes. In an alphabetic language the written form encodes the spoken one, so a learner who knows how a word sounds already has most of what is needed to write it, and a word met on the page can usually be sounded out and recognised. Each skill reinforces the others, and progress in one is progress in all. With Mandarin's character system, however, writing and reading must be mastered separately from speaking and listening. A character does not tell a learner how the word is pronounced, and knowing a word in speech does not reveal how it is written, so the two halves of the language have to be acquired through largely separate effort. That doubles the work at every stage, which is a serious obstacle for a language that would have to be learned by adults in very large numbers in order to serve as a global lingua franca. Mandarin's written character system will hinder its spread as a global lingua franca in a world dependent on technology. Technology for writing and the QWERTY keyboard are designed for the Roman alphabet, so the infrastructure through which most of the world writes already assumes a small set of letters combined freely. Global written media in the QWERTY keyboard is not compatible with the 2,000+ Chinese characters considered necessary for basic literacy in Mandarin, since no keyboard can offer thousands of distinct keys. In terms of a written language, English is much easier and adaptable.
Context
Mandarin is a notoriously difficult language for English speakers. Even as many linguists and businesspeople see the possibility of Mandarin becoming a more widely used, Mandarin will likely never become a global language because it is too difficult to learn.
Premises
Counter-arguments
No language is too structurally difficult to become a lingua franca. Languages become widely used due to the language becoming economically or politically necessary or through becoming culturally significant. In fact, though Mandarin's character system and tones are difficult to learn, Mandarin has several features that make it much easier to learn compared to European languages. Mandarin does not have subject/verb agreement, plurals, conjugations, or tenses. People do not have to fluently read and write Mandarin for it to be widely spoken People around the world do not fluently read and write English because they just use English as is necessary for their purposes, and English is still widely used. Professor at the Flinders University College of Humanities Jeffrey Gil stated, "The inconsistencies and irregularities of English’s writing system show that linguistic properties alone do not determine whether a language becomes global. I conclude that a character-based writing system will not prevent Chinese attaining global language status." Thanks to technological advances, written Mandarin is no longer a barrier to widespread Mandarin communication. Handwritten Mandarin is no longer a basic skill since smartphones and computers can generate characters from Pinyin Romanization or speech-to-text. Many Chinese people just use smartphone technology to communicate in written Mandarin.
Rejecting the premises
[Rejecting P1] Difficulty is measured relative to the learner's first language, and Mandarin is simpler than English on several dimensions — no inflection for tense, number or agreement — so the character system is one hard feature within a language that is not uniformly hard; English orthography is itself notoriously irregular, which shows a writing system's difficulty does not determine a language's spread. [Rejecting P2] The technological claim was overtaken by the technology it invokes, since Chinese text is entered on ordinary keyboards through romanised input and increasingly by speech, and full handwritten literacy is no longer required to communicate in writing — leaving the premise describing a constraint that the last three decades removed.