Islam is a set of ideas, beliefs and practices.
All from heaven -- to earth and beyond.
And Islam is a most complete, comprehensive, solid, sound and unassailable system, as it has to be if it is from God Almighty himself, the maker and master of the universe.
And Islam is not a hotchpotch of all kinds of good, bad, indifferent and hit-and-miss stuff, as it would be if it were the product of human mind and experience shaping it over centuries and across cultures.
Says the Qur'an:
Innaddeena Indallahil Islam!
Islam is the only system of life with the seal of approval from God.
Now, it is up to human beings, in every age and place, to examine Islam carefully and figure out if what I am saying here seems to make sense or not.