For starters, there is no historical evidence for the existence of Moses as a historical figure—i.e., a Hebrew raised as an Egyptian prince who flees into exile then returns to lead the Hebrews out of Egypt.
Secondly, the Exodus story is likely an embellishment of the forced exodus of a quarter of a million Canaanites from northern Egypt at the end of the Middle Kingdom period in 1550 BCE, which marks the beginning of the New Kingdom period. Even if they had a charismatic leader who might serve as the basis for Moses, casual but clearly assured graffiti inscriptions in a well-defined Canaanite/Old Hebrew script on statues in the western Sinai at that time support the evidence of Canaanites indicate that by this time, even ordinary folk (probably teenage boys, or young men) were literate in that script—which indicates that the script was invented a considerable time before that.
Sure enough, the oldest evidence of the emergence of a Canaanite script dates back to around 1800 BCE—a full 250 years earlier—on a rockface near the Valley of Kings, in Egypt proper:
Who that ingenious Canaanite was, we don’t know—a slave with some time on his hands (unlikely), an escaped slave (more likely) or a passing Canaanite trader (most likely)—but he was probably not someone high-born, else he would have made his inscriptions on a proper tomb wall, rather than a rockface, and the signs wouldn’t have been so crude.
Moses—insofar as he existed—led the Israelites out of Egypt, kept them alive in the desert for forty years, and laid the foundation of the monotheistic Judaic faith. I would say that’s achievement enough for one man. Give the credit for the alphabet to someone else.