Roman's reaction is based off of a backlash based off of accused (and somewhat rightly accused) nepotism. But if you don't think Vince is milking that reaction to suit his needs then you're probably watching the wrong programming. Vince always takes a natural reaction and adapts it if it serves his purpose. They did it with the Rock (who everyone HATED when he first debuted and got his first push) and they have been doing it with Cena for the better part of 10 years.
I think Roman might have had an easier time transitioning as the main guy if people didn't get the perspective that WWE was choosing him over Daniel Bryan.
I understand the nepotism argument and I am sure that has a lot to do with it. But I don't think that's the main thing right now. I think the crux of this hatred was the fans' perception that the WWE is telling them who to like despite the fact that the fans had already told WWE what they wanted. WWE kept pushing Reigns when Daniel Bryan was clearly the choice of the crowd. And yeah, Daniel Bryan had a reckless styles that was prone to injuries. But the majority of his fans (wrongly) didn't really care about that. They wanted to see him regardless.
WWE, on the other hand, wanted Roman. So it was an issue of the fans clearly telling WWE what they wanted and the fans thinking that WWE was telling the fans "We know better than you." People don't like being told what they should or should not like.
Daniel Bryan, however, quit being a factor when he retired. But fans are stubborn. Those feelings grew past Bryan and now are just a general feeling of "Don't tell us what to like." And so many people are clamoring for him to be a heel, but WWE isn't prepared to do that either. So to those fans, it's still telling fans what they should like. "You should like Roman as a face."
Personally, I don't think Reigns would have gotten a nepotism backlash if it hadn't been for the whole Daniel Bryan thing. But then again, I know a lot of people were also irritated when he won Superstar of the Year in 2014 despite doing little that year and being injured for several months.