So far you mentioned Messi, Neymar, Cavani, Robben, Griezmann. I suppose that means Ronaldo, Suarez and Bale are also up for discussion. Plus Hazard. But these players have very different characteristics and tasks in their team's offensive game.
So when you say this...
...it doesn't work at all for at least half of them. They aren't all at a similar level of technique, creativity, playmaking skills. So I already disagree with your basic assumption that scoring output is the only difference between world class offensive players.
If you read my post I explained why Cavani
wasn't one of them, despite being probably the best in the world at what he excels at, movement. Ronaldo, Suarez and Bale aren't up for discussion, because they score goals, it's really not that difficult to see the pattern. Role in a team or not, they all do the same thing- win games by scoring or assisting goals.
Ronaldo, Messi, Bale, Robben, Lewandowski, Neymar, Suarez, Griezmann, you name it. Regardless of what their role in a set up is, they influence matches and kill them off by being clinical. Take this into account, had you taken Costa out of Chelsea this season do you think they'd be so far ahead? Would Hazard's playmaking skills be enough assuming they had a less clinical striker, who was constantly squandering chances? I think it's safe to assume, no, they wouldn't. Hence why scoring goals is both the most difficult and most important part of football.
Playmaking is all good and well, Hazard is one of the best in the world at it, but he's a level below the elite who are much more lethal. I'm not just talking about scoring goals, I'm talking about being directly involved in them, either through finishing them or assisting them. The final ball is much more important than the build-up play before it. No-one gives a feck how you score, as long as you score.
He's great at what he does, but had he been in Neymar's boots in that PSG game for eg, with their backs against the walls, he wouldn't have had the ability or bottle to mount a comeback like Neymar inspired with the FK, that's the moments that Madrid would be wanting to pay that kind of money for, not for a faster and stronger Isco.