A word for a thing that is overlooked/a thing of negligence

Perhaps not the specific word you're looking for, but high-entropy seems to fit your definition.

Besides revolutionary (“something that portends of great change”), which it seems de rigueur to mention, consider terms like:
• scientific/social/cultural upheaval (“a sudden violent upset, disruption or convulsion”),
• groundbreaking (“Innovative; new, different; doing something that has never been done before”),
• radical (“Thoroughgoing”),
• breakthrough (“Any major progress; such as a great innovation or discovery that overcomes a significant obstacle”),
• the hyperbolic world-shaking (“Momentous; of great import; of great significance, importance or consequence”) or world-shattering,
• and the clichéd quantum leap (“discontinuous change of state” or “(metaphorical) An abrupt change”).