How good is Advantage in D&D?

Can we equate rolling with advantage in Dungeons and Dragons to a flat modifier? Let's ask this kenku we pulled off the street. Oh no, they're going on a long-winded tangent on probability...

(Note for commenters: I am aware that rolling a 1 is automatically a failure for attack rolls; however in 5th edition fail-on-1 for ability checks and saving throws is an optional rule, not an official one.)

This video was made for the Summer of Math Exposition π! The organisers intended to break for a year between SoME3 and SoME4, so there is instead a community-run version for this year. More information: https://some.3b1b.co

0:00 Modifiers vs advantage
2:05 Equating advantage to a flat modifier
4:51 Other questions about interpreting probabilities
6:42 Odds as a way of comparing probabilities
9:06 Conclusions