Ah man thats rough, one of the reasons I decided not to bother this year and give my ticket back was cause of crowd issues in 2017 when I last went and just nothing seems to be done despite it getting progressively worse year on year (And the BBC coverage had got me wanting to go back desperately)
The big "secret" sets need to stop , everyone knows the slots now, they are basically announced in advance so they are not secret and just lead to mad crowding. The other way you could handle them is when you have say someone like Diana Ross, why not have the Jack White, Georga Ezra "secret" sets against her to draw the crowd away? Some really bizzare choices in scheduling seemed to make the stages more crowded then they need to be, instead of painful clashes we used to get that split the crowd more.
And yeah you can't keep letting more people on site, without expanding the site and stage areas or expanding the facilities. Glasto isn't the the only space guilty of this though, many places with big crowds seem intent on shoving more people in than they can realistically handle.