The "This is Awesome" chant wasn't directed at Roman Reigns. It's literally that simple.
What a great point!
I love how you backed it up with empirical and anecdotal data.
Anyway, Reigns has fallen victim to being the only main event face in the company right now. I know that people are clamoring for Ambrose, but how exactly does that work when he wins? Ambrose is not effective being chased, he's effective chasing. At some point, he will have a couple of Jeff Hardy-esque one month reigns as the top guy, but you do not end Wrestlemania with a one month champion. Daniel Bryan, traditionally, would have been one of those champs, but his battles with the Authority would have allowed them to throw challengers at him for a while. Ambrose has been ancillary to all of the Authority storylines, but not a direct target of the Authroty's wrath.
Reigns downfall is not his in-ring ability. That is the WWE Main Event style. Daniel Bryamn was an outlier and Finn Balor will be when he gets to that spot. Watch HBK's title matches vs. HBK's midcard matches. The flippy shit was on the other matches. He adapted to brawling (with a few high spots to tide over his fans) when it was time.
Reigns downfall is not his lack of mic skills. He's acceptable on the mic and he is leagues better than he was a year and a half ago. His backstage "quick-hitter" promos are much better than his in-ring promos. If he can get the in-ring 5-10 minutes soliloquy promos up to the level of the 2-3 minute back stage stuff, he'll be fine.
Reigns downfall is not even his booking. HHH was always over with the live crowds, no matter his face/heel allegiance. We always knew he was Vince's guy. The internet felt he was burying everyone and hated him for a time, but the live crowds popped time and again.
Reigns downfall is his inevitability. He has the look, the lineage, and the endorsement to be the guy. That was apparent from their first powerbomb on Ryback. Reigns stood in the middle, stood tallest, and he was the one laid waste to Ryback. He is the one who kept the identity of the shield - Rollins and Ambrose changed. It was all all about him from the get go.
Sometimes he's cheered, sometimes he's booed, but he always gets a reaction. The same goes for Cena. Today's WWE superstars aren't judged based on whether they're getting the desired reaction, they're judged based on whether they're getting A reaction. WWE has to take it from there.
I do agree that he needs to be a monster heel. He should have been the one to join the authority and turn on Rollins and Ambrose. That would have gone over better. He could then make the face turn and reform the shield, and before I venture off into fantasy booking - ended the authority and retired HHH at this year's Wrestlemania.