Not all. Consider the Korean alphabet, invented by King Sejong the Great in 1443. From the Wikipedia:
In its classical and modern forms, the alphabet has 19 consonant and 21 vowel letters. However, instead of being written sequentially like the letters of the Latin alphabet, Hangul letters are grouped into blocks, such as 한 han, each of which transcribes a syllable. That is, although the syllable 한 han may look like a single character, it is actually composed of three letters: ㅎ h, ㅏ a, and ㄴ n. Each syllabic block consists of two to six letters, including at least one consonant and one vowel. These blocks are then arranged horizontally from left to right or vertically from top to bottom. Each Korean word consists of one or more syllables, hence one or more blocks. The number of mathematically possible distinct blocks is 11,172, though there are far fewer possible syllables allowed by Korean phonotactics, and not all phonotactically possible syllables occur in actual Korean words. Of the 11,172 possible Hangul syllables, the most frequent 256 have a cumulative frequency of 88.2%; with the top 512, it reaches 99.9%.
From King Sejong's Wikipedia entry:
Before the creation of Hangul, people in Korea (known as Joseon at the time) primarily wrote using Classical Chinese alongside native phonetic writing systems that predate Hangul by hundreds of years, including idu, hyangchal, gugyeol, and gakpil. However, due to the fundamental differences between the Korean and Chinese languages, and the large number of characters needed to be learned, there was much difficulty in learning how to write using Chinese characters for the lower classes, who often didn't have the privilege of education. To assuage this problem, King Sejong created the unique alphabet known as Hangul to promote literacy among the common people. His intention was to establish a cultural identity for Korea through its unique script.
King Sejong presided over the introduction of the 28-letter Korean alphabet, with the explicit goal being that Koreans from all classes would read and write. Each hangul letter is based on a simplified diagram of the patterns made by the human speech organs (the mouth, tongue and teeth) when producing the sound related to the character. Morphemes are built by writing the characters in syllabic blocks. The blocks of letters are then strung together linearly.
The Hangul alphabet was completed in 1443 and published in 1446 along with a 33-page manual titled Hunmin Jeong-um, explaining what the letters are as well as the philosophical theories and motives behind them. The Hunmin Jeong-um purported that anyone could learn Hangul in a matter of days. Persons previously unfamiliar with Hangul can typically pronounce Korean script accurately after only a few hours of study.