I agree with most of your arguments. But unfortunately disagree with the last part of your argument. The crop of racing drivers that make it onto the F1 grid, have come through various levels of fierce junior racing series where only highly talented drivers at these junior series make it through the ranks to be selected to have a seat in F1. From the very tough Go Kart series where so many really talented drivers do not make it through, to the various junior feeder series where a great many talented drivers do not make it to F1.
Just check out this go kart race to appreciate the level of talent that F1 drivers have to come through.
https://www.youtube.com/watch?v=xDgpS4kx88s
Getting into F1 is so incredibly hard. It takes great talent or billionaire dads to get into F1. For those that come from humble backgrounds, it has taken them immense sacrifices to land an F1 drive. These sorts of drivers are without any doubt the best drivers all the junior racing series has to offer. At any time, they represent the best drivers in the world. To dismiss their life journeys and sacrifices, dishonour them.
That said, there is always some doubt that other drivers in the grid in less dominant cars may have achieved the same things, given the chance in a dominant car. On the current grid, Russell or Leclerc or Norris or Gasly or Sainz in a Mercedes for instance. I remember us saying the same thing of Bottas in the Williams years ago. And how he has found Hamilton such a challenge with his opportunity.
Hence, to be great in F1 is not a fluke. I also do not think Vettel is representative of all multiple champions. Clearly, four consecutive title wins have burnt him out. The hunger of his early years in no longer there. That is not to suggest that he is an ordinary driver by any means.