I know this discussion isn't new ground (and I have absolutely no idea on numbers), but it definitely felt like a lot of people cleared off early this year.
The Pyramid post-Shania has to have been the most sparsely attended run on that stage possibly ever - we walked past not long after Burna Boy had finished and the crowd was taking up probably a third of the pit - everything I heard from people who were elsewhere was that it was pretty quiet, and even at Justice, where it actually was quite busy, we comfortably managed to get 3 off the barrier in line with the edge of the stage even with rocking up 15-20 mins beforehand
Deftones are not that expensive. Vilar de Mouros could book them and it's a much smaller festival. They were on the line-up for North Music Festival 2020, also a very small festival.
Can't speak to the Stones, but compared to Macca I'm pretty sure Elton was an absolute nother level. Purely anecdotal, but we were up at the very top in what used to be Row Mead by the Pylon for Elton and even up there it was absolute standing room only, Macca on the other hand we were about 75 yards in front of the tree and, whilst by no means empty, it was honestly pretty roomy for each group.
Will say though that that MacCartney set suffered from particularly extreme crowd crust, as when I went to the loo it was seriously rammed around the paths, with things "opening out" about 10 yards into the field