I've been going to Coachella, off and on, since 2001. A weak lineup is nothing new. 2002's lineup was a stinker, but in 2003 they followed it up with what I consider to be the most underrated and under-appreciated lineup in the history of this festival.
The only real change to the crowd over the years is the sheer size of it. Many of those who speak of a drastic change in the demographic of the crowd probably forget their early years attending when they were likely the insufferable ones they now hate. I know how awful I was when I first started going to Coachella, but now I am in my 30's and have moved on from the person I was in those days. It's ALWAYS ALWAYS ALWAYS drawn the insufferable college students and ravers. It's just that the culture of insufferable college students and ravers have sort of merged and altered in a way. Many of the vets around here now look at that crowd with the same disdain many older folks looked at them with 7-10 years ago or longer. In many people's eyes, roided out frat bros are just as insufferable as parachute-pant-wearing, drugged out e-tards, which is what littered the Sahara tent in the first decade of the festival.
Logistically speaking, Coachella does its absolute best to fix / correct any sort of issues. The attendance figures are high, but Coachella has mapped everything out to where you don't feel clustered in with a bunch of people often.
As far as not being as ambitious, I don't think that's the case at all. I believe they booked a lot of safe, popular acts (Muse, Skrillex, MGMT, Arcade Fire, The Glitch Mob, Calvin Harris, Alesso, Dillon Francis, Girl Talk, Chromeo and a few others) and that has ruffled the feathers of a few people, but there are zero or few other US festivals that are giving you The Replacements, The Knife, Bryan Ferry, Neko Case, Motörhead, Pet Shop Boys or The Afghan Whigs. Even many of the bigger festivals worldwide (Most notably Bonnaroo and Primavera) struck out on the Outkast reunion.
I can't really compare the experience to any of the other modern festivals, but I'll continue to attend Coachella, not just because it's the closest major festival to me, but also because it delivers year after year. Even my least favorite year (last year) was still a really good time. I will certainly take a year or two off sometime in the future (possibly to try other festivals) but as long as I can afford it and I can find enough in the lineup to be happy about, I will continue to attend.