I feel like the truth is somewhere in between what JM and Linty are saying.
Let's face it, when you book a babyface to win the main event at a major PPV and you KNOW he's going to get booed, rather than try some weak bs like bringing in his popular cousin, how about making a different booking decision? Even if they wouldn't yield on booking Reigns to win, at least turn him heel. Put Bryan in the top 2 or 3 and have Reigns eliminate him in controversial fashion and have him deliver a beatdown, for instance. That could perhaps set up a Bryan-Reigns match for your next PPV.
On the other hand, I think JM is right in that the modern fans are fairly horrendous. It's almost impossible for anyone to get a good pop anymore, outside of a small handful of guys. If they do get worked up during a match, it's only because of some spot. Great, let's all cheer for spot wrestling because that's so good for the long-term health and durability of your favorite wrestlers.