The stats don't really support this argument. For Utd this season Rooney's averaging 2.4 key passes per game (the most at Utd with Fellaini 2nd with 1.4), 2.2 crosses per game (the most at Utd with Valencia 2nd with 1.4) and 4 long passes per game (2nd behind Pogba with 4.3) and he's doing all that with better than 85% pass completion.
You know what a key pass is right. Rooney passes 5 yards to his right and a player shoots from 40 yards, key pass. Rooney flicks a ball over the top with a player racing to catch up to it, only just catching it on the line but 10 yards past the goal, he attempts to reach around it and cut it back, he ends up blasting it at the keeper because he can't get the angle to pull it back further... key pass.
Key passes don't directly mean anything, there is zero accountability for how or why someone shoots.
Also corners can count as key passes so if he puts the ball in and someone manages to touch the ball towards the goal... key pass. Someone who, contrary to his form, is both given the most important play making position/area of the pitch and takes most corners, a lot of freekicks and most penalties will have higher stats in all those key areas but it generally says exactly nothing about the quality of chances he one, creates from open play only and two, the quality of the chances he's creating.
A lot of stats are near meaningless without context and comparing them to other players in a similar position without knowing if one player takes all corners/penalties where the player being compared to them takes neither will give a misleading comparison. IE no.10 who takes corners and penalties might have on average 3-4 more goals and 5+ more assists a year than a no.10 who doesn't take penalties or corners.
Same with long passes, was it a 40yard ball up the field for a striker to run on to and creates a good chance, or a 40yrd completely pointless pass from one wing to the other. In general these are the worst and most pointless types of pass. Long floated ball, entire defence of the other team has exactly as much chance to readjust to the other wing and set themselves defensively. Rooney generally does the latter, runs out of ideas, knocks it long, wastes time and kills attack after attack with that style of passing.
Assists/goals still need context, though a pattern of high scoring is useful and stands out regardless of how easy the chances. Ultimately stats are a guide, nothing more or less. You want to compare strikers you use stats to find the top 10 highest scorers then look at all those players and make a decision for yourself about how easy the chances are. Maybe the guy with 30 goals got 7 penalties, 15 tap ins and only a handful of genuinely top quality strikes, his positioning and anticipation inside the 6yr box is great but he's limited and struggles in certain games... could maybe be someone like Giroud. Another striker gets 20, no penalties and has equally good ability to to be in the right place but scores from 30 yards, scores a few by taking on 3-4 players, scores some insane team goals where they are central to all the interplay and gets some of those easier tap ins as well, say Muller. If you went purely with goals scored you might decide Giroud is better than Muller(in some season where those numbers are true), and you'd be wrong.
All stats need context and considering them in context it's easy to see why Rooney can get such numbers, but watching any game with him playing in the last 1.5 and pushing 2 years now you can see that he's playing woeful football and it's easy to see where those numbers come from.