I wrote up a bigger post, but I felt like I was going on a tangent.
I think a large part of the reason why people don't get reactions is heels simply failing to generate heat. If they aren't doing things that make people dislike them then they won't get booed and people won't tune in to finally see when they get what they had coming to them. Now I'm not saying heel's should be booed for every single they do, but their job shouldn't be to win the crowd to their side. A heel should be taunting, mocking, calculating(working a bodypart for example) and sure they could be prideful and bust out a cool move, but only at the right times like when they believe they have the upperhand. It makes no sense for them to try and win the crowd over because that's the faces job. I know you feel there should be shades of grey, but that's only really effective at the right times. See: Shield vs The Wyatts.
And to be clear there's nothing wrong with liking the bad guy, but their wrestling psychology should reflect their character.