I agree with your entire post. The standard of the line up in 2024 should not be seen as the norm.
And in regards to Billie or Eminem I think the former is way more likely since we already know through Ken19 that Werchter tried to get her last year whereas Eminem has never played the festival before as I recall (or been rumoured).
I mean you had 1 headline that has just sold out a massive world tour including Wembley a couple of times, and a second headliner that sold out Wembley 10 times and has the second highest grossing tour ever.
The headliners in 2023 were weaker as a 3 than this year, it was only saved by Elton.
In this hyperthetical situation is there another festival in the UK consistently booking a bigger trio of headliners?
Only in that situation would I agree that it might lost its Kudos.
Given how mega popular O-Rod & Fred are right now - im not sure it should be making people feel uninspired by literally booking two of the biggest current acts int the world.