To some degree, I do agree that the crowd was annoying. Crowds like that can often be very annoying. Philadelphia is a very, very smarky wrestling town and many of said smarks can be extremely annoying when they don't get what they want.
Roman Reigns works hard, he's come a long way in the relatively short time he's been involved in wrestling, but a lot of fans are tired and frustrated of being told who they should & generally shouldn't invest their time in. What we've seen over the course of the past year or so especially isn't because of a couple of things here & there, it's years of pent up frustration with some of Vince McMahon's outdated perceptions and views. Vince McMahon feels that only a very specific type of wrestler should be at the top, namely one who either has or can have the look of a superhero. Roman Reigns is about 6'2 or so, about 250 pounds, handsome, well built, etc. Couple that with Vince sort of trying to tone down Reigns' edge over the past number of weeks with silliness and fans have come to the conclusion that he's essentially trying to create a younger version of John Cena. On top of it all, you have a guy that, compared to guys like Daniel Bryan, Dolph Ziggler, Dean Ambrose or Seth rollins, is extremely green. He's yet to distinguish himself in terms of promo capabilities, developing a rapport with fans, displaying charisma and significant capabilities of in-ring ability. In actuality, he's only been a singles wrestler in WWE for a total of 6 months or so, 2 of which he spent healing from a hernia and the surgery to repair it. Yet, in spite of all these short comings, he's in the main event of WrestleMania XXXI? That doesn't sit well with a lot of fans and it's hard to blame them. If they're not feeling the guy, if they're not willing to invest in him, then there's no money to be made. It's not Roman Reigns' fault, anybody in his position would love to have the spot he's been given whether they're "ready" for it or not. However, that doesn't change the circumstances that fans feel like they're getting another wrestler of the Vince McMahon formula pushed onto them, so why shouldn't they voice their displeasure at that?
I agree that there are some fans who can't be pleased. Hell, to be perfectly honest, I think there are some who want to bitch just for the sake of bitching. However, in this situation, there's no real excuse for WWE. It's not a matter of a few handfuls of fans not getting what they wanted, it's not a matter of just some "indie/internet darling" not getting the push a small contingent of fans feel he should get. Daniel Bryan is the most universally over babyface WWE has had in years. Men, women, kids, old & young all WANT to cheer for him, they LIKE cheering for him. Not everyone is a fan of him, that's how it is for every wrestler, but I think it's safe to say that a very clear majority of WWE's fans are fans of Daniel Bryan. They don't give a damn that he's not some 6'3" 250 pound stud, the fact that he doesn't fit with Vince's formulaic vision is part of the reason they like him. They like him on the mic, they like seeing what he's involved with and they like seeing him do what he does inside the ring and they don't see what the problem is. What they see is a wrestler who they feel has mountains more ability than the one being pushed and they're frustrated as hell over that.