I've no experience of booking festival line ups but I know enough about them to say that it's nowhere near as simplistic as many people on this forum believe.
All this talk about specific days being curated for a particular demographic, massively misses the main points which are a) when artists are available and b) what are they willing to do? If, for instance, LP or ORod are free that weekend, and RW want them as headliners, then the fact of the matter is they will book them on whatever day they are available. I doubt all these massive acts go to RW first every year and ask, 'When would you like us to play? All the other festivals taking place in Europe that weekend can work around you so just tell us what you want and we'll sort it?'
Reality is that the whole negotiation process is a big game of chess, with the main objective being to get the acts you want on your line up at a price that's agreeable. It's an added bonus if you can get them to play on a specific day but Glastonbury is really the only summer festival that has that sort of pulling power.
There's also far too many people making definitive judgements about the line up when it's nowhere near complete. If you don't like the look of it now, no problem - hold off for a bit but accept that it might sell out in the meantime and you can't go. The other alternative is to book your ticket now, knowing there's a chance it won't live up to your expectations - that's the gamble you take in these situations.
However, if you're into music and festivals then the likelihood is you'll have an amazing weekend whatever the final outcome is!