i won't pretend to be an expert but this is the internet so fuck it , my unsolicited opinions are
1. when a WR is going long and the ball is short its a timing issue between the QB and WR
2. when a WR is going long and the ball goes through the back of the end zone its a QB accuracy issue
3. when its a short throw and the QB hits someones feet its a QB accuracy issue
4. when its a short throw and it goes behind the WR its a timing issue between the qb and the wr
5. when it goes behind the wr near out of bands its probably a QB accuracy issue
now a scheme could make it more difficult to line all these things up, but i don't think thats the problem we've been seeing this year so far . Receivers are open the ball just doesn't consistently get to the right WR at the right time, place, or at all . or someone drops it , which is probably the WR unless they are thrown a missile or jump ball