The Top 4 teams listed are all West Coast offense teams which are short precision passing offense designed to get lots of YAC because that's how they move the football.
WC offense features lots of passes to RBs, Crossing routes, Slants, screens, etc. It was designed for weaker armed QBs who are very accurate on the short pass. The idea is to get rid of the ball fast.
Bills run a different Erhardt-Perkins system which features lots more deep passing down the field. You need a strong armed accurate QB to play in that offense but generally not a lot of short passing unless its a checkdown.
EP makes the QB look deep first, if nothing there, take the short checkdown.
WC makes the QB look short first and if nothing there go deep for a man to man coverage.
So why so low YAC ? Looking at the routes or route trees, Bills receivers ran almost exclusively tons of Dig routes.
That is the receiver runs down the field, turns around or starts running parallel to the LOS and Josh throws the ball right to him usually 40+ yards downfield. By that time the CB is on top of the receiver so not a lot of YAC. The CB has an easy tackle.
The question is why did Daboll call so many Dig routes ? I suspect that its the route that Josh is most comfortable throwing.
But no doubt implementing crossers, slants, screen, etc. will improve YAC.
But its not as bad as many are making it out to be. When your firing lasers 40+ yards down field you don't need YAC as much.