Why does Moses and the exodus story remain important for Christians today?

For at least three reasons:

It records the history of the nation of Israel.

It contains spiritual symbolism which is described in the New Testament.

It is referred to by Jesus, directly and indirectly in a number of places. For example:

14And as Moses lifted up the serpent in the wilderness, even so must the Son of man be lifted up:15That whosoever believeth in him should not perish, but have eternal life. 16For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.