They say Buddhism is the only atheistic world religion. That may be true, but lots of supernatural, metaphysic, and eschatological nonsense has accreted to Buddha's core message across the centuries of cultural evolution.
Despite the many cultural accretions, there is something admirably ingenious about Buddhism's fundamental reframing of the issue of death in its philosophy. Most religions blunt the psychological potency of the awareness of the inevitability of personal mortality with a promise of everlasting spiritual afterlife. Buddhism does something much more extraordinary and difficult.
Buddhism presupposes an immortal afterlife, but conceives it as a terrible punishment (karma), and a terrible chore, not a reward. Then it makes its highest ideal the extinguishment of the self (nirvana) and an end to the cycle of rebirth (personal death), which adherents actively strive for. In essence, Buddhism combats the existential angst resulting from the knowledge of personal mortality by making personal mortality its highest ethical achievement instead of just a biological eventuality. This is fine mental judo; making a virtue of something you cannot change.
This is why Buddhism is my favorite world religion. It wraps the kinds of mythic meaning and rituals we humans hunger for around a core of practical atheism and self-reliance that I wholly endorse.